Bill and Hillary Clinton were the most sought after surrogates in the Democratic Party this year. He campaigned for more than 47 candidates. She for more than 26. Supporters estimate that, together, the Clintons headlined 75 rallies and fundraisers — and logged roughly 50,000 miles jetting from state to state.

When the Clintons travel, they fly private. This year, their airfare cost candidates at least $699,000, available state and federal campaign finance reports show.

Payments from campaigns and party committees to Executive Fliteways, the independent charter company the Clintons use, could be found for just under half of the trips the former first family took on behalf of Democrats this year.

The costs of two Clintons trips — one to Iowa, the other to Kentucky — were reported earlier this fall by Bloomberg and Politico, respectively.

But the $699,000 figure is the first comprehensive estimate that establishes the scope of the costs associated with using the Clintons as surrogates. By the time the rest of the filings come in, the number will likely exceed $1 million.

The Clintons couldn't have paid for their own flights. Legally, candidates are required to pay for surrogate travel or report the costs as an in-kind contribution.

But not every campaigner flies on private charter planes. Sen. Rand Paul, who was on the road nearly every week this fall on behalf of Republicans, often flies commercial — and in coach. He travels alone or with one aide. In contrast, Mike Huckabee, the former governor who sold himself as an American everyman, racked up thousands in private air travel bills, as Politico reported this year.

For the Clintons, flying commercial isn't as viable an option.

Both fly with multiple members of their Secret Service security detail. (One person familiar with the former secretary of state's travel arrangements said she is usually accompanied by about four people from the detail.) Staffers also typically accompany the Clintons on their trips. At rallies on the road this year, Hillary Clinton often appeared with at least three aides from her personal staff.

As of this week, filings showed there were 32 total expenditures, some made in installments of two, made this year by campaigns to Executive Fliteways. Most of the finance reports that show expenditures made after Oct. 15 — when the Clintons did a large share of campaigning — are not yet available to the public.

Only candidates and committees that the Clintons supported showed disbursements this year to Executive Fliteways, which is based in Ronkonkoma, New York, on Long Island. No other candidate or surrogate appeared to make use of the charter company. The 32 payments were each recorded in filings for a campaign or party just before, or soon after, a Clinton event for that entity.

The costs — which total $699,172.82 between both Clintons — are based on a review of 2014 filings to the Federal Election Commission and to secretaries of state, with use of the Congressional Quarterly Political MoneyLine database.

The millions the pair raised at fundraisers far surpassed any travel expenses candidates had to cover. Every rally with a Clinton also garnered attention from the national press — valuable earned media for campaigns.

But the Clintons benefited from the trips too. The former secretary of state, who is considering another run for president, reintroduced herself to voters this fall on the campaign trail and honed a new stump speech.

The average cost for each Clinton trip was roughly $21,000.

Most of the listings for the flights are recorded in finance reports under a memo like "travel expense" or "airfare." A handful of the expenditures listed by the campaigns with more specific notes — like "Charter Flight - WJC" or "Flight - HC 10/16/2014."

Bill Clinton, who campaigned aggressively for Democrats from the spring to Election Day, racked up the majority of the costs that are so far public. Filings for 25 of his events show he billed campaigns at least $610,370.30 for his air travel.

Because Hillary Clinton held most of her rallies and fundraisers in late October, only a fraction of the expenses associated with her travel are currently public.

Payments for the seven trips for which filings are available show her travel cost campaigns at least $88,802.52.

One joint event with her husband at the Iowa Steak Fry, an annual fundraiser hosted by Sen. Tom Harkin, cost $50,099.82 in airfare.

That bill was first reported by Bloomberg last month. The tab for another Clinton trip, an Oct. 15 visit to Kentucky on behalf of Alison Lundergan Grimes, who lost her race for Senate, was first reported earlier this month by Politico.

Executive Fliteways owns a fleet of private jets and has three bases across New York, including one at the Westchester County Airport in White Plains — a 15-minute drive from the Clintons' home of 15 years in the hamlet of Chappaqua.

Public flight records show a Falcon 900 jet housed at Executive Fliteways charted the same course as at least two Clinton trips this fall. The company's website features a picture and description of the plane, which seats 12 passengers.

Clinton has considered basing her possible presidential campaign out of White Plains, Politico reported this month. If she does put her headquarters there, the Westchester Airport could serve as a convenient travel hub for the campaign.

A list of the costs associated with the 32 campaign trips is included below: