What really caused this incident is trying to put 7 pounds of sugar into a 6 pound sack. And the need for speed. Hurry up all you pilots or the chief pilot will get mad at you for being late.
IF you are on the ground, the need for speed STOPS. Parallels to Teneriefe are about right. WAS there any question in the cockpit? IF SO, don't move, clarify the clearance.
Get on the radio and confirm: Tower, DELTA XXXX VERIFY takeoff clearance for DELTA XXXX on runway XX.
Midway airport is a funny airport. Its operations are dictated more by nearby o'hare airport than its own needs. Add to that performance limited runways and things are hanging on by a thread.
Its hard to see what is going on , on the other runways with the mk1 eyeball too.
Well, it worked out and it was interesting to hear old Southwest cover themselves first.
I can imagine a scenario in which the radio calls were covered just enough to make sense to both planes/pilots