My last post was in response to Martin Wolf.
As for surving a cruise altitude of 29,000 ft without oxygen. Not likely. Climbers carry supplimental oxygen for mountains that high.
It’s not quite that simple. An aircraft is vulnerable any time it’s on the ground, not just when it’s on the ramp during a turn-round. Some airfields have poor security fencing where someone can clamber into the wheel well when the aircraft is on hold (when waiting for take off permission). Especially at night for instance, and especially if you’re desperate.
V
Vetch, Point taken. Time to break out the infrared gogles. Or you could put camera’s in all the wheel wells for the pilots to watch. Might make for smoother landings to see the runway up close.
Personally, I’m a little more worried about climb-out.
You don’t want the pilots watching the wheel wells - they need to watch where they are going.
Put an infrared detector in the wheel well. If it registers something of human body temperature, THEN be suspicious.
(Then all you have to worry about are inanimate objects being inserted into that area…)
I’m not sure how effective heat sensing devices would be in distinguishing a human body in the wheel bay of a modern airliner. There are other sources of heat being generated there. Apart from the brake units which generate and retain heat, other components are situated in the wheel bays- flap motors, gearboxes etc. They all produce heat.
I tend to agree that a camera might be useful, (and I do know that approaching take off is a busy time for a pilot)
Having worked at Heathrow for some time I have seen how El Al approach this problem. The aircraft is followed by a security vehicle until it reaches the runway. There is no opportunity for late arriving passengers 
- or, hopefully, an inanimate object.
V