I was told they were limited to FL290 because the skin was too thin to take more pressurization.
and
The 146 is certified to FL310 or FL300 depending on model. They're limited to FL280 simply because they are not RVSM capable.
Utter crap!
The max operating altitude depends on the pressurisation system fitted.
If you have a BAe Dynamics analogue system, it's FL300 or FL310.
If you have an NGL analogue system, it's also FL300 or FL310.
However, if you have an NGL digital system fitted, the max operating altitude is FL350.
FCOM 2.2.13 for anyone who doesn't believe me...
And the airframe is plenty strong enough to go higher than that, being British...
Also, the only thing you need to do to a 146 to get RVSM approval is fit proper digital altimeters. That fixes all the altimeter inaccuracies that have always plagued the 146.