In reply to BoredTired&Lazy:
Most cheap airfare companies (a'la SLeazyjet and RiistoAir) will often not end up being feasable with pads.
Mid-sized ones (Moon Warrior or so sized) will often fit in the maximum sports equipment dimensions, but can still be spendy. Bigger pads, it depends.
The best I've found is Norwegian, for whom even the gigantic Organic Big Pad will fit (with stuff stuffed between... or two such behemoths tied together even) and even two Warrior sized pads strapped together will be fine. And no extra costs (as in it is considered a normal baggage, so might be included in the fare). Naturally, extra baggages will be extra, but for shorter trips that's fine (clothes, shoes etc will fit just fine in the carry-on).