Manchester airport always seems to have at least two armed officers patrolling airside even through covid times, these officers also walk along the piers pass the departure gates especially in terminal 1 which is some distance from the main departure area with shops/bars etc
Seems to me there was two reasons in incident at Luton, One the airport doesn't want to pay for policing because passenger numbers are very low due to covid, this is absolutely disgraceful if you lower your guard your more prone to attack (terroist or any other) remember airport busy or not are always a target
second police and security should be airside at all times,bars are always open at airports which could attract trouble although not in this incident, what if it had happened nearer to a departure gate and they forced the doors open and gone onto the airfield,