The reality of modern life is that there are few, if any, reasonably well paid uneducated, unskilled jobs any more - those went out with union powers in the 1980s.
If your lad is not well suited to education, then training (becoming "skilled" - a term which traditionally meant having completed a craft apprenticeship) is the way ahead.
Apprenticeships still exist in many fields, including aircraft engineering - although the competition for them is clearly fierce. Academic qualifications are part of the equation, but more importantly your lad will need to show a real enthusiasm for the area of work - which in aviation means either maintenance, or design/build (one of the most sought after, for example, is at Westland Helicopters - details are usually on their website, another excellent one is with the various MoD establishments supporting whatever activities go on there - try Boscombe Down for example). [This is despite an academically snobbish educational establishment doing it's best to brainwash kids into believing that only the academic route to advancement is worthwhile.]
So, the best advice that I can offer (and I've done both routes - apprenticeship then academic) is that yes, aircraft engineering has got potential to be a great career - but it's not an easy option, and the only people who'll find their way through are those who are enthusiastic enough to really WANT this career. That applies to both routes. So, probably the best you can do for your son right now is to help him find something he really wants to do, and then everything you can to foster that enthusiasm - in whatever area of activity he wants to aim at.
I've got two (step)sons, now 17 and 23. The older is the less academically bright of the two, but was directed - he knew (knows) what he wanted and now has a good degree and is developing a career in his chosen direction. The younger is brighter than his brother and (I'd judge) probably cleverer than me (and I've got a doctorate). He however has failed at every junction to find anything he really wanted to do, as a result scraped poor GCSEs, got thrown out of sixth form college for not working, and looks about to repeat the trick elsewhere - leaving him unemployed and unemployable, to the deep frustration of all around him.
So for my money it's motivation that counts, not academic ability. If he can find it, the Northbrook course (or an apprenticeship) may suit very well, and even if he then decides it's not what he wants to do, may suit him to future career choices better than a degree would.
And if he's not going to do anything specific with them, why on earth should he waste two years doing A-levels?, which are intended as university entrance qualifications anyway. He'd be far better off doing something, anything, that's actually vocational.
(Sorry for the lecture, but as you may guess I've developed strong views on the subject.)
G