I have been getting a few questions on eBay (NIB 19") about the tire clearance for the Flight. I took some measurements and pictures of my personal bike:

Pumped the standard 2.1 Maxxis Ignitor rear tire to 35 psi:

At the same spot I measured the chainstays opening:

For comparison I measured a 26" 2.4 MK from my GT expert:

Hope this helps somebody.