ROUGH LANDING: British lawmakers question Heathrow Airport's ability to handle an influx of passengers during the London Olympics this summer, warning that long lines at immigration could force planes to sit on runways or circle Europe's busiest airport before landing.

EARLY WARNING: Last year, even without the crush of the Olympics, Britain's former border chief relaxed some passport checks during the busy summer tourist season just to handle the demand.

SKY HIGH: Heathrow typically handles an average of 190,000 passengers arriving and departing each day, with 69.4 million total in 2011.