Sen. John McCain (R-Ariz.) has traveled extensively for his presidential campaign this year on airplanes provided by several of the large corporations he helps regulate as chairman of the Senate Commerce Committee.

McCain has paid a dozen corporations and wealthy donors for use of their private aircraft, according to a review of his campaign disclosure reports. The trips, for which McCain paid more than $40,000, ranged from a quick jaunt to Richmond on the private plane of CSX Corp. for a fund-raiser at the home of the railroad company's chairman to a California flight aboard a plane owned by a U.S. subsidiary firm of media mogul Rupert Murdoch.

McCain, whose influential panel has jurisdiction over a broad array of businesses from telecommunications to transportation, has also flown in private jets owned by the phone company BellSouth Corp. and the Union Pacific railroad. A spokesman said that, in most instances, McCain's campaign asked the corporations to provide the aircraft.

Such flights are a routine matter for many influential members of Congress, who take advantage of federal rules allowing campaigns to fly in private planes as long as they pay the companies, in advance, for the cost of first-class airline tickets--a generous benefit, since those fares are often far less than the actual cost of operating the private planes.

But it is a unique irony of this year's presidential contest that the two most frequent corporate fliers have been McCain and Democratic hopeful Bill Bradley. Both are running as outsiders, focusing their campaign rhetoric on the need to reform a political system that gives undue access to big contributors, while they have used their ties to wealthy backers to bring in campaign money and line up private flights.

Their establishment rivals have had no need to turn to corporate aircraft. Vice President Gore flies aboard Air Force Two, with his campaign paying the government for his political trips, while Texas Gov. George W. Bush has state aircraft available as well as a massive campaign bank account to pay for commercial charters. Bush's campaign has also paid several corporations for use of their planes to fly supporters to Texas.

McCain's use of corporate planes is particularly noteworthy because of the influence he wields over a wide variety of American businesses as the Commerce Committee chairman and his identification with the issue of campaign finance reform. But his campaign said it is precisely because McCain does not have the trappings of incumbency, unlike Gore or Bush, that he must turn to private planes.

"Not having access to government planes, like others do, we took advantage of every other plane we could to arrange for travel," said McCain spokesman Howard Opinsky. "In each of the cases, we called to arrange for travel because we couldn't find commercial flights that met the scheduling demands that we had at the time."

McCain himself has publicly and frequently bemoaned the system of unlimited "soft money" contributions from corporations, wealthy individuals and unions to political parties. He argued on the Senate floor last month that "all of us are tainted by the system" in which big donations "buy access."

While many of the corporations whose jets he borrowed are among the biggest soft-money givers, Opinsky said McCain makes a distinction between "the influence that a $100,000 contribution is able to buy" and the "very carefully regulated system" under which corporate flights for candidates are allowed.

But members of McCain's party have expounded at length on the benefits of being able to reimburse the airplane travel at only the cost of a first-class fare. In attacking first lady Hillary Rodham Clinton's use of government aircraft, which is reimbursed at that rate, Republican National Committee Chairman Jim Nicholson described it as a "tremendous advantage" that allowed her to avoid the cost of chartering a plane.

The corporate trips pose an uncomfortable dilemma for campaign finance reform advocates who have worked closely with McCain and Bradley. "The practice is wrong, and the rules should not allow it," said Fred Wertheimer of Democracy 21, who has pressed unsuccessfully to require campaigns to pay higher rates for such flights. But Wertheimer also said, "Both Bradley and McCain have established they really are committed to reform. It's a real priority for them."

Bradley, who for years served on the Senate Finance Committee, has taken "approximately 45" trips on corporate aircraft, according to spokesman Eric Hauser, most frequently on planes owned by Jordan Industries, an international conglomerate based in the Midwest, and New York deal-maker Herbert A. Allen's investment firm. Overall, Bradley's campaign reported more than $55,000 in "travel expenses" that appear to be for corporate flights.

Hauser characterized the flights as a case of "ardent supporters of Bradley and the campaign offering to help," adding, "I would dispute the presumed connection between advocacy of campaign finance reform and the use of private aircraft. Throughout the campaign, we've made clear we're going to set a higher standard, and we're going to abide by it."

Another corporate flier on the campaign trail is, like McCain, a Senate committee chairman. Utah Republican Orrin G. Hatch, a late entrant in the presidential race and head of the Judiciary panel, has paid about $19,000 to the pharmaceutical company Schering-Plough Corp. for several trips on its corporate jet. Schering-Plough is seeking to extend the life of its patent for the anti-allergy drug Claritin--an issue before Hatch's panel.

Hatch's disclosure reports included other possible corporate jet payments, such as a $900 payment to Health South, which the campaign refused to explain.

In McCain's case, the corporate jets have ferried him to events all over the country--New Hampshire stumping tours, an Atlanta fund-raiser, a book promotion appearance in Wichita, a veterans convention in Kansas City.

Union Pacific flew McCain from Seattle to Omaha to Los Angeles for a total cost of $4,820. The railroad company's former chairman, Drew Lewis, used his own plane to send McCain on another trip, to Hilton Head, S.C. And the firm's top lobbyist, Mary McAuliffe, has been a major fund-raiser for McCain here.

April 19 was a typical corporate flying day. BellSouth's aircraft picked up McCain and several staff members in New Hampshire and flew them to Atlanta. According to a company official, McCain spoke at an "employee forum" at the telecommunications firm and then went to a fund-raiser sponsored by other local business leaders. The next day, the plane flew back to Washington with McCain, his aides and one company executive. Total cost: $5,458.

Staff researcher Ben White contributed to this report.