McCain, with a laugh, said he told Harry "I've never seen, in all the years I've been here, such an unbalanced gender crowd."
From there it was on to the White House for a previously unannounced visit with the first lady, Vice President Joe Biden's wife, Jill, and military mothers and children at an afternoon tea. Harry joined with the children in helping the kids make Mother's Day gifts from tulip and rose bouquets, vegetable chips and edible dough jewelry gathered in the State Dining Room.
For the prince, the Washington settings were a world away from the Afghanistan war zone where he recently served for 20 weeks as a co-pilot gunner in an Apache attack helicopter. It was just as far removed from his hijinks in a Las Vegas hotel room last summer, when fuzzy photos got out of a naked Harry playing strip billiards.
McCain, R-Ariz., who was shot down over North Vietnam and tortured as a captive, said he told the prince that "he was probably a much better pilot than I was."
As for the prince's reputation for cutting loose on occasion, McCain joked that the British diplomatic reception and dinner later in the evening was sure to be a "wild and raucous affair."
On Friday, the prince visits Arlington National Cemetery and Walter Reed National Military Medical Center before flying to Colorado for the 2013 Warrior Games in Colorado Springs. More than 200 wounded servicemen and women from the U.S. and Britain will participate.
Harry will also visit parts of New Jersey afflicted by Superstorm Sandy and stop for events in New York City before capping his visit by playing in the Sentebale Polo Cup match in Greenwich, Conn., on Wednesday.
Diana highlighted the work of the mine-clearing charity HALO Trust when she was pictured wearing a face mask and protective clothing during a visit to a minefield being cleared by the trust in Angola in 1997. Fiona Willoughby, marketing manager of the trust, said the prince's tour of the trust's exhibit raises the profile of the issue once again.
"People have forgotten about it, and we think Prince Harry, following in his mother's footsteps, is a worthy cause and will raise the profile of what we are doing," she said.
Harry closely quizzed trust officials on mine-detection techniques and photos of amputees, keeping a somber if animated tone despite the swooning throng held back from the exhibit area.
The prince "seemed to be a little the word isn't embarrassed it was, I think, a normal reaction," McCain said. "I'm sure it's not the first time."