dead pan your #17
Farnborough could be an option if he wanted to fly the flag for US aerospace industry
..except Farnborough will be holding its 2018 Airshow from Monday 16th July until 22nd July, so not very likely IMHO.
ISTR that the last time a president visited he landed at a USAF air-base in east Anglia and flew down to London in the presidential helicopter.