MeatEater’s Campfire Stories, volumes 1 and 2
First into Action, by Duncan Falconer
Cabin Pressure, volumes 1-3
Danderlust, by Peter Ross
Woodsman, by Ben Law (if you can get over him talking about “roe stags”!)
Combat Crew, by John Comer
Typhoon, by Mike Sutton
Last Man Standing, by Roger Moore
Carrier Pilot, by Norman Hanson
Under the Knife, by Arnold van de Laar
Mustang Ace, by Robert Goebel
First Light, by Geoffrey Wellum
Of Living Valour, by Barney White Spunner
Uncommon Valor, by Stephen L Moore
Across an Angry Sea, by Cedric Delves
A Handful of Hard Men, by Hannes Wessels
Painting the Sand, by Kim Hughes
All of the above are worth listening to.
For a long flight you might want to try the MeatEaters Camp Stories, as it is is broken up into separate stories of about 10-15 minutes each. Similarly the Cabin Pressure series is made up of 30 minute episodes, each of which is a gem!
If you enjoy the older Radio 4 comedies in general then I can also recommend The Adventures of Hamish and Dougal, Old Harry’s Game, Revolting People and Bleak Expectations. The original I’m Sorry I Haven’t A Clue still has me in stitches.