Both the number and range of rockets used against Israel has increased compared to prior cycles of violence (or whatever better neutral term you would prefer). Iron Dome isn't perfect and even hitting a single U.S. flagged aircraft, loaded with fuel and passengers, no matter the death toll, simply isn't worth the risk. To make matters worse, how about an Iron Dome missile that hits a plane, for whatever reason, or caused part of an inbound rocket to hit a plane, etc.
The political games that would be played after even a near-miss, both within the U.S. and internationally, should be obvious.