isn't it more likely that this was an attempt to send large letter bombs to the addressees?
Of course it was; it was no more an attack on an aircraft as it would have been an attack on the mailvan that finally delivered it.
It was a low-level and silly attempt; so silly that there must be a suspicion that it was a diversion or had some other ulterior purpose.
Al Qa'ida has much bigger fish to fry than a building used by some Jews.