WASHINGTON (AP) — When Joe Biden was running for president three years ago, he flew on a white private jet with his campaign logo painted on the side.

Now he has a larger, more recognizable ride as he seeks a second term. Like his predecessors, he'll be crisscrossing the country on Air Force One.

Every president blends their governmental and political duties, but never more than when they're running for reelection. "Official" events can sound especially political, while "political" events can delve deeply into the policy initiatives of the day. And decisions on how to divvy up the costs of a president's travels between taxpayers and the campaign is no simple task.

Biden made one such trip this week, his first since formally announcing his campaign, when he spoke about his economic agenda at an official event north of New York City before heading to Manhattan for a pair of fundraisers.

"I'm determined to finish the job," Biden said to about two dozen donors in an Upper East Side townhouse. Then Biden zipped over to a Fifth Avenue apartment, where more wealthy supporters sat on couches and chairs in a grand living room surrounded by artwork.

"I want to thank everyone here for the help," he said. "Without you guys, I wouldn't be standing here."

The massive logistical and security apparatus that surrounds a president continues no matter where they are or whether they're on government or political business. Even mundane trips require an assortment of helicopters, armored cars and other vehicles and staff to ferry the president, aides, security personnel and journalists from place to place.

By longstanding practice, the vast majority of those costs are borne by taxpayers, a smaller amount picked up by Biden's campaign or the Democratic National Committee.

"It's well established, and there's a pretty intricate set of formulas," said Norm Eisen, who served as a White House ethics lawyer under President Barack Obama.

Yet piecing together how much taxpayers will be on the hook for to fund a president's campaign travel is far from clear-cut. Many of the true costs pertaining to transporting and securing the president are classified, and even the formulas used to determine how much the president's campaign has to reimburse the government are difficult to scrutinize.

Federal regulations guide the calculations, which look at the share of the president's time spent on the ground devoted to political and official activities. And rules require that government flights like Air Force One are reimbursed at higher rates for a similar flight aboard a charter airfare instead of commercial flights.

For every trip, it's up to the White House counsel's office to determine what percentage is political and the amount of reimbursement, officials involved with the process said. And it's a time-honored practice by presidents in both parties to tack official events onto political trips to defray the cost to their campaigns.

But even official events can get plenty political as presidents push their agenda. On Wednesday, Biden used his official event to criticize "MAGA Republicans" for "holding the economy hostage" in the standoff over the debt ceiling, which could lead to the country defaulting for the first time in history.

When it comes to paying back the government for travel, "it's always somewhat of an opaque process for how it's reimbursed," said Aaron Scherb, senior director of legislative affairs at the watchdog group Common Cause. "It's a little bit more of an art than a science."

The Democratic National Committee has a special escrow account where it collects travel reimbursements that will eventually be sent to the U.S. Treasury. For example, after Biden went to Florida to attend a fundraiser for Charlie Crist's ill-fated campaign for governor last year, Crist's campaign deposited $27,726.95 into the account. Then-Senate candidate Val Demings' campaign kicked in another $23,610.51 for a joint rally that evening with Crist's campaign, which came after an official event meant to highlight his efforts to lower drug prices for seniors.

That combined sum was a small fraction of the cost to send Biden from Washington on Air Force One and by helicopter from near Fort Lauderdale to Miami Gardens.

The helicopters that operate as Marine One when the president is on board cost between $16,700 and nearly $20,000 per hour to operate, according to Pentagon data for fiscal year 2022. The modified Boeing 747s that serve as the iconic Air Force One cost about $200,000 per hour to fly. That's not to mention the military cargo aircraft that fly ahead of the president with his armored limousines and other official vehicles.

All told, more than $2.8 million has been deposited in the escrow account for travel since Biden took office in January 2021, according to Federal Election Committee records. However, because of the slow pace of government processing, only about $133,000 has been relayed to the government.

The current generation of Air Force One planes date back to President George H.W. Bush's administration, and two replacements are currently being built. Even if Biden wins a second term, he's unlikely to have an opportunity to fly on them before leaving office — they're scheduled to be delivered in 2027 and 2028.

Administration officials said that the Biden White House and the campaigns his travel benefits comply with all federal rules and precedents.

But the cost of presidential travel often becomes a target in an election year.

For example, then-House Speaker John Boehner complained after Obama spoke to college students during official events in battleground states while running for reelection.

"His campaign ought to be reimbursing the Treasury for the cost of this trip," Boehner said.

President Donald Trump adhered to rules on reimbursements for campaign travel during his failed bid for a second term. However, he drew scrutiny for blurring the lines in other ways. For example, he used Air Force One and Marine One as backdrops for political events, and he would direct the plane to be flown over his rallies to energize supporters.

Trump also accepted the Republican nomination in a speech from the White House, a controversial use of federal property for political purposes.

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Associated Press writer Seung Min Kim in New York contributed to this report.