Nazir 55a. If a person is carried into Chutz Laaretz in a box, Rebbi holds he is tamei and Rabbi Yossi ben Rabbi Yehuda (RYBY) holds tahor. The dispute hinges on whether a tent carried by people or animals can shield a person from the defiled earth over which he is floating. But if the tent is flying in the air, not carried by anyone, even RYBY agrees that it does not shield him. Thus RYBY said: If one had a big box of utensils and threw it over a dead body, the utensils inside are tamei, but if the box was standing still, they are tahor. (Tosafos, second explanation)
נזיר נה ע”א: לא, דכולי עלמא משום גושא, מר סבר: אהל זרוק שמיה אהל, ומר סבר: לא שמיה אהל. והתניא, רבי יוסי ברבי יהודה אומר: תיבה שהיא מלאה כלים וזרקה על פני המת באהל ־ טמאה, ואם היתה מונחת ־ טהורהִ.
תוספות: אהל זרוק – שנכנס בשידה שבהמה או אדם מוליכים אותו שמיה אהל לחוץ ולהפסיק, וצ״ל דעדיף מטלית המנפנפת דתנן במס׳ אהלות (פ״ח מ״ה) דאין חוצצין בפני הטומאה ואין מביאין, והיינו טעמא דהכא עדיף משום דרגלי האדם או הבהמה הנושאים השידה והתיבה נוגעים בארץ אבל הטלית מנפנפת באויר, ומר סבר אהל זרוק לא שמיה אהל והיינו דאמר והתניא בניחותא.
The Shvus Yaakov was asked the following question: a kohein lived in one of a ring of attached houses that all opened onto a central courtyard. Someone died in one of these houses, so the kohein left his house and stood in the courtyard. But he could not exit the courtyard to the street without passing under a roof connected to houses. Does he have to stand there under the open sky until the body is removed, or is there some permitted way for him to get out?
The Shvus Yaakov quotes the above explanation of Tosafos, that RYBY holds that a carried tent protects, and only a flying tent does not protect. The Rashba rules like RYBY, so this kohein could be carried out in a large box (at least 3 cubic amos in volume). The Rambam, however, seems to give contradictory rulings: in Tumas Meis 11:5 he follows Rebbi, but in Nezirus 5:18 he follows RYBY. The Shvus Yaakov proposes that the halacha follows RYBY on a Torah level, but on a Rabbinic level we are strict like Rebbi. Therefore, even the Rambam would agree that the kohein could be carried out, because human dignity supersedes a Rabbinic prohibition.
The exact wording of the Rambam in Tumas Meis 11:5 is:
הנכנס לארץ העכו״ם בשידה תיבה ומגדל הפורחין באויר טמא, שאהל זרוק אינו קרוי אהל.
Given that the Rambam says explicitly “flying in the air,” it is puzzling that the Shvus Yaakov did not resolve the apparent contradiction in the Rambam by saying, as Tosafos does, that when the box is literally flying through the air, it does not shield, but when carried it does shield.
The Chazon Ish (Yoreh Deah 211:5) argues that the Rambam in Tumas Meis could not have meant a literally flying tent, because then he would be neglecting to pasken on the question of a dragged or carried tent, which is the subject of the dispute between Rebbi and RYBY. Rather the Rambam means a carried tent. The Rambam didn’t bother addressing a real flying tent because that can’t happen in real life, except by the powers of a Shem or by throwing.
The Chazon Ish asks: what about the doors that were placed on top of oxen when the children went to draw water for the Parah Adumah? (Tosafos in Eiruvin 31a asks this question on Rebbi and responds that Rebbi will disagree with that Baraisa. But the Chazon Ish’s question is on the Rambam, who rules like Rebbi, yet says that the doors were used.) He answers by quoting the Mishneh Lamelech who says that since it was only a chumra to protect the children from tumah, they were lenient. The Chazon Ish explains that they relied on RYBY, as perhaps this was a dispute going back to the Bayis Sheni times too.
Based on the above, the Chazon Ish rules that a car or train moving over a cemetery does not protect its riders from tumah. And all the more so that an airplane, which is not supported by anything, would be considered a flying tent, so a kohein is not allowed to fly over a cemetery.
The Tzitz Eliezer 12:62 allows a kohein to ride in a bus on a road built over a cemetery. His reason is that he understood the Rambam in Tumas Meis to mean that a “flying tent” does not shield from tumah only when it is literally flying, but when supported by people, animals or wheels, it does shield.
In summary, the Chazon Ish is the strictest opinion here: he does not even allow traveling in a car over a cemetery. The Tzitz Eliezer is the most lenient, while the Shvus Yaakov takes a middle position, forbidding it only Rabbinically and therefore allowing it in cases of human dignity. But all three poskim agree that a kohein is forbidden to fly in the airplane over a cemetery.
This issue became a practical one late in the summer of 2001, when a newly-observant Israeli pilot asked a number of halachic authorities: How is it that kohanim are permitted to embark on flights leaving Ben Gurion airport that pass over the cemetery in Holon? Upon investigation it was discovered that this had been a problem since 1984, when flight patterns were altered to minimize flying over densely populated areas north of Ben Gurion airport and to avoid overflying a military area south of the airport. Rav Yosef Shalom Elyashiv, Rav Shmuel Halevi Wosner, Rav Nissim Karelitz and the Badatz all ruled that it would be forbidden for kohanim to take those flights.
In February of 2012, the problem deepened when the north-south runway at the airport became unusable, and all flights began using the east-west runway. Under international law, a runway can only be used in one direction at one time, for both inbound and outbound flights. At times of the day when the runway was being used for westbound traffic, the takeoffs were not a problem, as they flew directly west out over the Mediterranean, but the landings were a problem: the flight path to approach the airport led directly over the cemetery, after which the pilots made a U-turn and approached the runway from the east. At times when traffic was eastbound, the departing flights made the same U-turn in the opposite direction and passed over the cemetery.
When the problem was discovered, some kohanim began wrapping themselves in plastic bags during takeoff and landing to shield themselves from tumah. This led to shock and fear among other passengers, as well as endangered the kohanim themselves, since the plastic bag was not allowed to have any air holes, and it would be difficult for them to access oxygen masks if necessary. Many flights were delayed because the crew refused to allow kohanim to use the bags.
After much negotiation, the religious community prevailed upon the airport authorities to have the pilots alter their flight path slightly to avoid the cemetery. However, this was only possible during the day, when the pilot controls the airplane manually. At night, the arriving pilots have to be electronically guided into the airport, as they do not rely on visual directions. All incoming flights have to locate a beam, and the beam then takes over control of the plane from the pilot and guides the plane to the runway.
What about changing the beam system to guide the plane to avoid the cemetery at night? The authorities were not willing to do this, because they preferred that the nighttime flights pass over the vast Holon Cemetery, rather than over residential areas where the noise would be a disturbance.
It was noted that many American-bound flights take off between 12 and 1 AM, at which time the runway is used in the westbound direction, so these flights were not an issue.
[The question here is why anyone would think that a plastic bag does any good. Just as the plane does not shield the kohein from tumah because it is a flying tent, the plastic bag is also flying and has the exact same problem. Perhaps the answer is that the Chazon Ish (Yoreh Deah 211:9) adds that even if we were to follow the opinion that a flying tent is a tent, the airplane, as it is made of metal, does not shield its passengers from tumah. Thus the plastic bag would solve the problem at least according to this opinion. However, as we have established above, the halacha is that a tent that is literally flying is not a tent, so the difference between metal and plastic is academic.
This does come into play in a bus or car, where there are some such as the Tzitz Eliezer mentioned above who permit a kohein to ride over the cemetery. The Tzitz Eliezer advises that since the vehicle is made of metal, it is preferable for the kohein to place a flat wooden board under himself while passing over the cemetery.]
Source: dinonline.org, yated.com.