British Airways pilot kept the secret

From the NY Times:

On the flight over, Air Force One had come within sight of a British Airways plane, Dan Bartlett, the White House communications director, told reporters on the trip, according to the transcript.

The British Airways pilot radioed over and asked, Mr. Bartlett said, "Did I just see Air Force One?" There was silence from the Air Force One pilot, who then replied, "Gulfstream 5."

There was a longer silence from the British Airways pilot, Mr. Bartlett said, who, seeming to get that he was in on a secret, then said, "Oh."