Kohanim Flying on Airplanes
The problem of kohanim flying on planes over cemeteries has been reported widely; this article is not meant as a responsum, but simply to explain generally the halakhic issues involved. As the halakhot of taharot are not broadly studied even among the most ardent talmudists, ignorance of this topic is rampant. One must note that this prejudice against Seder Taharot is not new and there is a scarcity of material, posing a formidable challenge for both the layman as well as the moreh hora'a. Actually, it is the only seder of mishna without either Talmud Yerushalmi or Bavli (with the exception of Masekhet Nida, for obvious reasons). This gap was not appreciably closed by subsequent generations. I have seen modern responsa on the topic by otherwise competent poskim, and found them riddled with mistakes and fundamental misconceptions. I hope I do not fail in the same manner. This article will try to explain the issue in general terms. [A hebrew version, with a more in-depth treatment, can be read here.]
A dead body generates a special form of tum'a which does not apply to other sources of tum'a (with the exception of a metzora): tum'at ohel. There are three cases in which tum'at ohel applies: 1] when a person, utensil or food are under the same ohel ("tent") as the corpse; 2] when the corpse is above any other object; and the one we will deal with here: 3] when one goes above the corpse. In each of these cases, any objects or individuals become tamei. The definition of an "ohel" is "tefach al tefach al rum tefach" - a structure of a volume of one square handbreadth with a space of a handbreath between it and the corpse. An ohel can have two functions:
1] The spreading of tum'a: someone who is under the same ohel as the corpse is tamei, even if he is not directly above or below the corpse.
2] Separation: somebody situated above the ohel is tahor, even if he is directly above the corpse.
There are some ohalot that serve both functions, some that only spread tum'a, and some that do neither. (See Ohalot ch. 8.) Another aspect unique to corpses is the prohibition against kohanim coming in contact with them. Although there is a minority opinion that since kohanim are already assumed tamei, there is no prohibition against their contact with corpses, this opinion has been roundly rejected halakha le-maaseh. (There are two possible explanations: 1] the contact itself is prohibited, regardless of any additional tum'a; 2] immediate contact results in an intensification of the tum'a). This is one of the few practically relevant, halakhic ramifications of taharot. (The other areas are netilat yadayim, sekhakh and ketamim of a nida.)
The gemara in Berakhot 19b relates that under certain, extenuating circumstances, kohanim may walk over coffins since in most coffins there is an ohel of a handbreadth. Unfortunately, according to the vast majority of rishonim that provision does not apply to a tomb. Any closed building containing a dead body is defined as a tomb for purposes of this halakha. Hence, the space of a tefach does not block the tum'a and it extends skyward to anything situated directly above the tomb. Rashi in Nazir (52b) represents the dissenting view, but the Rambam, Ra'avad, Rashba, Tosafot, Ramban, et al cite strong proofs against Rashi's position from various texts. The tum'a of a tomb thus extends skyward - much to the consternation of priestly travelers.
Could the plane itself block the tum'a for the kohen? Two different approaches need to be investigated: 1] ohel; 2] tzamid patil. As we mentioned before, an ohel can separate from or block the tum'a. Can the space at the bottom of the plane, since it measures more than a handbreadth above the source of tum'a, serve as an ohel to block it? This heter encounters two problems: 1] ohel zaruk; 2] anything that is tamei cannot block tum'a. Let us deal with each problem separately. The mishna in Ohalot (ch. 8) addresses a situation of an ohel in motion, such as large boxes during transport, and determines that such an ohel loses its formal status as such. It is considered an ohel for neither spreading nor blocking tum'a. The gemara in Eruvin (30b) determines that this issue is debated by the tanna'im. Tosafot and the Rambam concur that an ohel in motion cannot block tum'a. Though there might be some exceptions (see Tosafot there), it is unlikely that any would exclude an airplane. However, the Rashba prefers the opinion that an ohel in motion can block tum'a; according to the Rashba, then, this problem (of ohel zaruk) is solved. The second problem arises from the general rule that anything that is tamei or can become tamei cannot block or separate from tum'a. Can an airplane contract tum'a? Rav Moshe Feinstein deals with this issue (with regard to the related issue of a corpse transported on the same plane as a kohen). The question revolves around the issue as to whether aluminum, which, together with its alloys, constitutes 80% of a plane's weight (my thanks to Dr. Farber, an eminent metallurgist), is susceptible to tum'a. On the one hand, metallic utensils are generally assured capable of contracting tum'a. On the other hand, the Torah mentions only the six metals that were known to man at that time. Can tum'a apply to metals that were discovered only after Matan Torah? Rav Moshe wavers on this very issue, and also questions whether aluminum is a new metal or a combination of the six mentioned. Scientifically, we know that aluminum is, in fact, a new metal, and not a composite of other metals.
As for Rav Moshe's first question, this point is not new and seems to be a dispute between the Rambam (who holds that all metals are tamei) and Rashi (who limits tum'a to just the six mentioned). The Vilna Gaon and Tiferet Yisrael concur with Rashi, and in the introduction of the Tiferet Yisrael to Taharot, a parenthetical comment of unknown origin questions the limitation to the six metals. (Interestingly, in another responsum about tevilat kelim, Rav Moshe determines that aluminum is not tamei as a metal utensil, but it nevertheless requires immersion as it is included in the rabbinic requirement to immerse glass utensils.) Therefore, there is a clear opinion that aluminum objects are not tamei. The existence of rivets or other parts of the plane can be overlooked so long as all the major components are aluminum or carbon composites. There might be another possibility, that ships are not defined as "utensils" capable of contracting tum'a because of their size; this may apply to airplanes, as well. As this possibility is speculative at best, it certainly would not merit a heter on its own right, but it may be included as an additional consideration when reaching a final conclusion ("senif le-hakel").
In order to accept this heter, both assumptions must be correct. We must assume that an ohel in motion is an ohel, and that airplanes are tahor (for any reason). As we noted, however, both assumptions are not at all clear; this heter thus leaves much to be desired.
Another possible heter involves the halakha of "tzamid patil." I struggled to come up with a proper translation and eventually gave up; I will nevertheless try to explain it. If a sealed utensil is in an ohel with a corpse, it and its contents remain tahor. Of course, this is not so simple. There are certain prerequisites for the application of this halakha: 1] The utensil cannot be mekabel tum'a from its exterior. This halakha is thus limited to earthenware utensils (which contract tum'a only from the inside) and utensils which are not mekabel tum'a at all, such as stone or mud utensils. The inclusion of aluminum planes, then, depends on our previous discussion as to whether they are susceptible to tum'a.
2] It must be closed and sealed with a lid and a material such as mud, wax, dough, etc. We may consider several reasons why such a seal is required. Two logical reasons might be a requirement for a hermetical seal or for a seal which is not easily opened. One could reasonably argue that the seal of airplanes fulfill this requirement since the door seals are hermetic (hopefully) and cannot be opened during flight. However, given the subject matter in question, it is hard to rule out the possibility of a gezeirat ha-katuv - that the requirement for a seal made from the aforementioned materials - provision constitutes an edict with no explanation. I have not found any definitive indication in either direction.
In summary, there are two possible bases for a heter: 1] ohel 2] tzamid patil (a sealed utensil). Both, however, are faulty on two accounts, one that they share in common and another unique to each. The common problem involves the tum'a of airplanes themselves. The heter based on ohel encounters the problem of an ohel in motion, and the tzamid patil heter raises the question regarding the nature of the seal required.
How, then, should we deal with this question in pesak, in determining the final halakha? Although it is hard to consider either heter as certain, perhaps both together should yield a lenient ruling. At first glance, the operative principle we should follow here should be "safek de-oraita le-chumra" (we rule stringently in situations of doubt concerning Torah law). On the other hand, perhaps we may consider this issue a situation of sha'at ha-dechak, extenuating circumstances, which allows reliance on a minority opinion. A leniency on these grounds, however, would naturally apply only to travel for certain purposes and barring reasonable alternatives. We might also consider the rule, "safek tum'a be-reshut harabim tahor" - any questionable instance of tum'a in public areas is considered tahor. However, the application of this rule to our case is far from clear. Although the plane is considered a public area, we must take into account two other issues: 1] does the prohibition against kohanim coming in contact with dead bodies follow the guidelines of the laws of tum'a, or of standard issurim? The Minchat Chinukh leaves this as an open question; the Marcheshet and the Noda Be-Yehuda took compromise positions regarding this issue. The provision of "safek tum'a" would apply in our case according to the Noda Be-Yehuda, whereas the Marcheshet would render it inapplicable. Rav Yitzchak Elchanan Spektor applied it hesitantly (if two other authorities would agree) to the issue of trains riding over cemeteries. Our issue, regarding airplanes, bears some similarity to the issue of trains (ohel zaruk and the dispute between the Rashba and Tosafot), but, in some respects, differs. Some of these differences render the situation of planes more problematic (trains have direct contact with the ground), while others render it less problematic (planes have a better chance of being tahor since they contain major components of aluminum). There seems to have been a minhag in Jerusalem for kohanim to place a board underneath their car when they traveled to Jericho, a trip that required passing over part of the famed cemetery on Har Ha-zeitim. This minhag is more difficult to justify than either allowing one to travel without a board or forbidding the trip even with a board. Some Acharonim (Penei Yehoshua and Shevut Yaakov) claim that on the level of Torah law, an ohel in motion is an ohel; it is only as a result of rabbinic enactment that we do not consider it as such. This would thus allow room for leniency in cases of doubt. This position, however, though widely quoted, seems to my mind very doubtful. If this were true, then an ohel in motion should spread tum'a, just as it blocks it (recall our earlier discussion as to the two different roles of an ohel), and this is clearly not the case.
Where does that leave us, if not altogether confused? Hopefully, it leaves us with an understanding of both positions and a bit more knowledge of the fascinating and complex world of taharot. Sometimes it is better to be perplexed and confounded rather than confused.
The proposed solution of wrapping oneself in a large bag on the plane would encounter both problems discussed. One needs a "utensil" which is not mekabel tum'a (a large plastic or nylon bag would do) and it must be sealed; the easiest method would probably be to seal it with duct tape. Of course, we are not interested in producing another corpse on the plane. We may, however, propose an ironically simple solution. Paradoxically, only the opening must be sealed; there can be multiple holes in other places of the "utensil." Thus, one can simply cut holes in different places in the bag.
That is as far as the dry halakha is concerned. The gemara in Sanhedrin relates that Rebbe Yehuda Hanasi refused to grant Rav the authority to rule on certain matters even though he knew the halakhot perfectly well, as he was afraid that he would be misunderstood. In the position of posek, one must consider the public effect of his decisions. The gemara on many occasions rules, "halakha ve-ein morin kein" - the halakha is clear but we must not issue such a ruling. Perhaps today the danger is greater, as we, as observant Jews, and, more seriously, the halakha and Torah are constantly subject to ridicule (by both the malicious and the ignorant). I am sure the original rabbis who issued the edict would have done otherwise had a reporter asked their opinion, but it was in any event inevitable that such a psak would be publicized. If the posek can find no way to allow travel over cemeteries, perhaps alternate routes could be explored, but the proposed solution is a nonstarter for reasons of chilul hashem. In Avot (1:11) Avtalion says: Wise men, be cautious with your words, lest... the name of the Lord be desecrated."