What if she leaves a couple days earlier, delivers the planes, and then takes a more northerly return route to head back to Pearl. At some point in the afternoon on December 6th her scouts detect signs of the Kido Butai and in return her task force is also detected.
How does Nagumo respond?
How does the Lex respond?
What does Pearl do when alerted?
The Lexington would have to take a VERY meandering return route to get her anywhere near the course of the KB. Maybe she could have been given a secondary assignment for after Midway plane delivery to see whether she could get into place to do a real time exercise to try and detect the B-17s in course on December 7th heading for Oahu? Its a tenous POD, no doubt.
The POD states the spotting occurs in the afternoon. Depending on how late in the afternoon (after 2pm? even earlier?), would it even be possible for either side to launch a strike before it gets too dark to land the returning planes?
I think Nagumo would move ahead with a strike on Pearl for the 7th anticipating it already being on alert. Also on anticipating an alerted Pearl, could he launch scouts pre-dawn, say 4am-ish to be in place over Hawaii at dawn to see whether the US fleet has already sailed and if so where. Then he could divert the strike toward a sailing US fleet.
No doubt if there is an air battle with the Lex, she is going to get sunk.
Were the planes delivered to Midway in addition to the Lexington's normal plane contingent, or is she now down an air group?
IMHO, the Lexington would be insane to do anything other than call it in to Pearl and get the hell out of dodge.
Pearl would unfortunately send out its Battleship line and they would get severally mauled. Is the higher loss in life of experienced, trained sailors more important than actually losing the antiquated battleships? IOTL, where did the surviving shipless sailors get reassigned to? There must have been thousands of them.
Despite getting the Pacific Fleet mauled, there would be higher damage to the planes and crews of the Kido Butai. How much more? What's the tipping point in damage for making it worthwhile to "sacrifice" the Pacific Fleet's battleships? Twice, three, four times the damage as IOTL? And how damaging could it be to their later operations at Wake Island and in the DEI and the Indian Ocean?
Is saving Wake by the Kido Butai not being able to detach 2 carriers for the second attempt worth 6 sunk battleships and 5,000+ dead sailors?
Another poster also mentioned they'd burn more fuel, and they were already at the end of their logistics tether.