Three F-16s roared toward Fenway Park, flying wingtip to wingtip. Suddenly a fourth F-16, trailing behind the formation, caught up, flew under the three F-16s, then looped up and over the formation to take its rightful spot for a perfect V formation.

The maneuver, performed during the Red Sox Opening Day game Tuesday, came just as the Boston Symphony Orchestra finished playing the national anthem. It elicited roaring applause and cheers from the full-capacity crowd, which clearly appreciated what it thought to be great showmanship. But as it turns out, the maneuver was improper and the Vermont Air National Guard grounded the pilot this week.

"I understand the crowd liked it, but you won't see it again," said Lieutenant Colonel Lloyd Goodrow, a Guard spokesman.

The pilot, whose name was not released, conducted the maneuver to slow down after he raced to catch up with the formation already in progress, Goodrow said. But the pilot, he said, was flying at an altitude too low for such a maneuver: about 1,100 feet, rather than the sanctioned 5,000 feet or higher.

"Our highest responsibility is safety," said Goodrow, although he quickly added: "At no time during the flyover was anyone in jeopardy. . . . He's a very professional pilot, and he was in control of the plane at all times."

He also emphasized that the maneuver was not acrobatic, as it has been characterized by some spectators.

The pilot's sudden maneuver concerned at least one fan, Gina Reitano, a 39-year-old Fall River resident who sat behind the bullpen on Opening Day.

"I thought that maybe he was having trouble with the plane," said Reitano, noting she has seen four other flyovers previously that didn't include such a dramatic maneuver. "I didn't think there was any imminent danger but just that maybe something was wrong."

"The people around me were drunk so they just went, 'Whoaaa,' " she added.

John Blake, Red Sox spokesman, said the team fielded no complaints about the maneuver and hasn't had a chance to talk to the Guard about it.

"I'm not an expert on flyovers," Blake said.

"If something was amiss, I wouldn't have known."

The pilot will go through remedial training before being allowed to fly again.

Amalie Benjamin of the Globe staff and Globe correspondent Sarah M. Gantz contributed to this report.

© Copyright 2008 Globe Newspaper Company.