BA318
Birmingham and Manchester to Scotland cannot be done in under 3 hours on train.
London to Scotland or vice versa cannot be done in under 3 hours on a train.
Southampton to Manchester or Scotland or vice versa cannot be done in under 3 hours on a train.
Newquay to any domestic Flybe destination cannot be done in under 3 hours on a train.
Not sure why the "3 hours by train" argument is even being brought up. That's also dependant on times and availability of train tickets, which are often more expensive than domestic air fares, and with many train operators running reduced services.