"The fastest ever time for the crossing, the fastest ever set by a passenger aircraft, was 2 hours 52 minutes and 59 seconds. This was set by Captain Leslie Scott and his crew onboard G-BOAD, flying from New York to London, on the 7th of February 1996."
Just because there were no private Concordes in our world doesn't mean Lex didn't have one. Obviously, he picked Lois up about noon on a Saturday, and they were at a restaurant in Milan by eleven pm, local time. I know I've gone out to dinner in London at 10 pm and the place was packed with a queue outside, so eleven might not be as unbelievable a dinner hour there as here. Then he had her back home by midnight her own time.
