Mr. Isham and other news executives say they remain committed to the White House beat, but they are looking for new and less expensive ways to work. Mark Whitaker, the Washington bureau chief for NBC News, said, “We still cover the president as thoroughly and responsibly as we always have; we just have to look at the best way to do it, both logistically and financially.”

Presidential trips cost the press about $18 million last year, according to the correspondents’ association.

“The prices are exorbitant,” said David Westin, the president of ABC News. Seats on a press charter plane can run $2,000 for a domestic flight and tens of thousands overseas. ABC appears to be watching costs as it reshapes the news division, which eliminated 25 percent of its staff positions this spring.

The news outlets vote on whether to charter a plane, but it’s not easy to get the majority: The big television networks — ABC, CBS, CNN, Fox News and NBC — represent five of seven votes. (Mr. Chen casts the other two votes on behalf of other correspondents.) When the networks choose not to travel in a pack, reporters of all stripes have to make other arrangements.

The skimping on charters started in the tail end of the George W. Bush administration and has deepened during Mr. Obama’s 16 months of office, particularly in the last three months, news executives say.

In these cases — be they in Buffalo this month or in Prague, where Mr. Obama traveled last month without a press charter for an important nuclear arms deal — the only reporters who are in the so-called presidential bubble are the dozen in a travel pool that fly on Air Force One and take notes and pictures for the rest of the press corps.