U.S. hotels are vulnerable to lodging demand declines greater than those last seen post-9/11

, according to PKF Hospitality Research. A PKF study found a direct correlation between airline capacity and lodging demand. If the number of airline seats flown domestically falls by 10 percent, lodging demand could potentially dip 3.9 percent, whereas after 2001 it fell 3.3 percent, PKF reported.