If you consider the times of 4 people taken amongst 50,000,000 , sure it's perfectly possible. But if you reduce that number to 4 known people who should make a known action and who can not contact each other, and who can not control their own startup time, it becomes impossible.
Sigh...
What you are really saying is: If you clock the arrival, coffee-drinking of any 4 customers, the result will be impossible. It is only possible if 50,000,000 customers go to the cafe.
Last saturday, the German lottery drew the following numbers:
10 - 11 - 16 - 21 - 41 - 46
How do you think this was this possible, when there are about 14 million different possibilities? Or do you think it was impossible to draw these numbers, and there is a conspiracy going on?
Man, get the clue: When 4 planes take off, level off, get hijacked and crash, there MUST be some timeline that emerges. This timeline is as possible as any other. It is extremely likely that the planes will take off in succession, level off in succession, be hijacked in succession and crash in succession when there is no central coordination. Because the only alternative to all this happening in succession would be that some things happen precisely at the same time!
Now, if all planes had been hijacked at the same time, then yes, we would have reason to suspect some kind of fine co-ordination. Because out of the 50,000,000 possibilities, maybe only 5,000 have simultaneous events, and 49,995,000 have successive events.
Another example:
Invite 4 friends separately for dinner at 20:00. Would you expect them to arrive in succession, or would you expect them to arrive at the same time?
If they arrive at the same time, would you think they co-ordinated their arrival (maybe travel together)? If they arrive in succession, would you then think they co-ordinated their arrival (maybe travel together)?
Another example: Again, invite 4 friends, but not to your place, but to 4 different restaurants. This time, they live in 3 different towns and take 4 different trains. When the train arrives ("level off"), they must hitch a taxi ("hitchhike") to get to their respective restaurants ("crash").
Would you be surprised if the trains depart in succession? Would you be surprised if the trains arrive in succession? Would you be surprised if any or all of the trains were delayed? Would you be surprised if one is more delayed than the others? Would you be surprised if your 4 friends take different amounts of time between arriving at the trainstation and hitching a taxi? Would you be surprised if the taxis needed different amounts of time? Would you be surprised if your friends arrived at their restaurants at different times (in succession)? Would you be surprised if the one who started his journey first already hitched a taxi when the last one's train just started? Would you be surprised if the one who started first arrives first, and the one who started last arrives last?
All of which I described here accurately descibed what the terrorists and their planes did on 9/11. And nothing at all there is surprising!