A dirty little secret is that MANPADS aren't particularly effective against commercial airliners; the warheads are too small. The majority of commercial airliners that have been hit with them have survived (and they have mostly been smaller aircraft in Africa.)
You mostly take out one engine and commercial airliners are designed to survive the loss of one engine.
Actually they're not particularly effective against anything other than helicopters.
In fact they are ineffective against airliners not because of a size of a warhead which is sufficient to knock any engine but because of a short range. Manpads are simply short legged to catch up with aircraft cruising at 30,000 altitude.
Helicopters aren’t an easiest target which are actually a low flying fighter-bombers. Twin engine aircraft are less vulnerable as you can find on many videos from Chechen-Russian war on YouTube.
In fact commercial airliners might make good targets on departure as well. It is certainly not a best time to lose an engine.