Updated

A flock of small jets took flight from Washington Thursday, each carrying a Democratic presidential candidate to South Carolina for the first debate of the political season.

For Sens. Hillary Rodham Clinton, Barack Obama, Chris Dodd and Joe Biden, it was wheels up shortly after they voted in favor of legislation requiring that U.S. troops begin returning home from Iraq in the fall.

No one jet pooled, no one took commercial flights to save money, fuel or emissions.

All but Biden, who flew on a private jet, chartered their flights — a campaign expense of between $7,500 and $9,000.

Federal Election Commission rules allow candidates to pay only the equivalent of first-class fare to fly on private jets owned by corporations or other special interests. But a Senate ethics bill approved earlier this year would require senators flying on corporate jets to pay full charter rates. The legislation must still be reconciled with a House bill and has yet to become law.

Several senators running for president are abiding by it anyway, either paying charter cost or avoiding corporate jets altogether, as Obama and Republican Sen. John McCain have done. Dodd pays full charter rates when he flies on private planes. The Clinton and Biden campaigns did not immediately explain their policies.

Candidates who follow the more lenient FEC rules have a financial advantage.

Democrat John Edwards, for example, regularly uses a jet owned by Dallas trial lawyer Fred Baron, who is also the finance chairman of his presidential campaign. His campaign pays first-class rate for those flights. Republican presidential candidate Mitt Romney also flies on corporate jets and pays first-class rates.

Under FEC reimbursement regulations, a candidate flying in a corporate or union jet must pay the first-class rate unless the flight's destination does not have scheduled commercial service. In that case, the candidate must pay the cost of chartering the plane.

For candidates who are now eschewing corporate jets, the cost difference can be significant.

For example, a one-way first class ticket on United Airlines with four days advance notice is $694 per person. A typical one-way charter flight on a small Lear jet seating six people would cost about $9,000.

Critics of corporate jet flights for politicians say the difference in cost makes a private jet an extraordinary special benefit and can give corporate executives or union leaders unusual access to a candidate.

Thursday's debate, set on the campus of South Carolina State University in Orangeburg, S.C., made for some whirlwind scheduling. Clinton, for instance, was scheduled to return to Washington Friday morning for an 8 a.m. address to the New York State United Teachers 35th Annual Representative Assembly, then fly back to South Carolina for an 11 a.m. event in Greenville.