Kedusha of the Airspace over Har HaBayis
8. Balcony protruding over Har HaBayis. The poskim explain that the airspace over Har HaBayis also has kedusha. Thus, rooftops and upper floors on Har HaBayis have the kedusha of Har HaBayis (מנ''ח סוף שסב, שו''ת הרדב''ז ח''ב תרצא ). One should therefore not enter an upper floor or balcony built around the Beis HaMikdash that protrudes into the airspace over the site of the Beis HaMikdash.
9. Flying over Har HaBayis. One may not fly through the airspace over the site of the Beis HaMikdash in a plane or helicopter, even at a high altitude, because the Azara’s kedusha also exists in the airspace above it, all the way to the sky (שו''ת באר משה ח''ז קו' עלעקטריק סי' ק', צפנת פענח פ''א הל' תרומות ה''ו, הר הקודש עמ' שכ''ט ). Thus, those who fly over Yerushalayim in a helicopter must be careful not to fly over the site of the Beis HaMikdash (הגר''י כדורי הוזכר בשערי ציון ח''ג סוף סי' כ''ז ).
10. Unmanned aircraft. Also, one may not fly an unmanned aircraft, e.g., a drone, based on the halacha that one may not throw tamei items into the Beis HaMikdash (רמב''ם פ''ג ביאת מקדש הט''ז ). All metal items can receive tumah from people (שו''ת קנין תורה ח''ג סי' נ''ח, הגריש''א, קו' הליכות והנהגות לבין המצרים ).
Tunnels and Channels under Har HaBayis
11. Tunnels under Har HaBayis. Even one with tumas zav or baal keri may go in underground tunnels beneath Har HaBayis, as the tunnels do not have kedusha, and the kedusha of Har HaBayis does not go all the way down through the earth. However, tamei people may not enter tunnels that also extend under the Azara and open up to the Azara itself, as those have the status of the Azara itself (שו''ת רדב''ז סי' תרצא, הר הקודש עמ' שכט, שו''ת צי''א ח''י סי' א ).
12. Thus, one should be careful today to avoid entering the tunnels that go under Har HaBayis itself out of concern that they open up to the Azara.
13. Kosel tunnels. However, the “Kosel tunnels” that are open to the public today are outside the Kosel and Har HaBayis, so entering them poses no halachic problem (ספר הכותל המערבי פ''ד עמ' מ''ו ).
