from Bols:

There is not exactly a RAW line that allows Flying Monstorous Creatures to Deep Strike, but the old Tyranid FAQ said Harpies and Hive Tyrants could if they purchased the Wings upgrade. The problem is that the FAQ didn't specify whether the wings made the MC an FMC and granted the Deep Strike special rule, or that the FMC could Deep Strike because of what it is.

But, up until 14 days ago, Tyranid FMCs could deep strike.

There's even an FAQ for the rulebook that clarifies which mode Deep Striking FMCs enter the battlefield in, but strictly read it would only apply to FMCs with the Deep Strike special rule.

From an RAI, it's clear that FMCs can, but an RAW doesn't say they can. RAW only says what happens if they do. I'm sure the new FAQ will allow it again, but only time will tell.