Washington ? Authorities were concerned with terrorism threats in the air and on the ground Saturday. The British government delayed a London-to-Washington flight for three hours and U.S. officials monitored heavily secured stadiums playing host to the first round of professional football playoffs.

British Airways 223, the most scrutinized flight since the United States declared a high terrorism alert Dec. 21, lifted off from Heathrow Airport just after noon CST Saturday after intensive security checks and landed safely about eight hours later.

It took nearly an hour for all the passengers to get off the plane and make it to the terminal area at Dulles International Airport in suburban Virginia.

“There was a lot of security, but we felt it was necessary due to the sensitivity of what was going on here,” passenger Joel Ginsburg told WTTG-TV in Washington. He said there was nervousness among passengers, “but the BA people were very good and reassured us the security was tight as a drum and we were going to go for it.”

“It was somber,” he said of the preflight mood in London. “It was like you could hear a pin drop in the gate area.”

Other routes under scrutiny during the code orange alert in the United States were London-Riyadh, Saudi Arabia, and Mexico City-Los Angeles.

Homeland Security Department spokesman Brian Roehrkasse said Saturday that authorities had been discussing security with the National Football League and the National Collegiate Athletic Assn. during the playoff and college bowl season.

NFL playoff games Saturday were in Baltimore and Charlotte, N.C., with contests today in Green Bay, Wis., and Indianapolis. There were weekend bowl games in Boise, Idaho, and New Orleans.

NFL spokesman Joe Browne said security had been tight since the Sept. 11 attacks, and air space over stadiums was restricted by federal legislation.

He said security for the Super Bowl, which is Feb. 1 in Houston, would be even more intense because of the international attention the event receives.