For Cabinet secretaries, such as Health and Human Services Secretary Tom Price, the decision to fly on private airplanes instead of easily available commercial routes has put their standing in the administration in question. Price's actions prompted deep anger from Trump, who is steaming over the matter, thinks the use of private planes is "stupid" and is considering whether to fire his health boss, multiple sources told CNN.
Price's vow Thursday to repay only a fraction of the estimated $400,000 it cost for his charter flights only appeared to exacerbate Trump's anger. People familiar with his thinking said the President thought the move was half-baked and only fueled the story further. An evening appearance on Fox News, in which Price described his repayment as "unprecedented," caused eye rolls and groans among Trump's top aides.
A presidential ally said on Friday that although Price could be pushed out soon, there is concern within the White House about replacing him. Among the options being considered: Food and Drug Administration Commissioner Scott Gottlieb and Centers for Medicare and Medicaid Services Administrator Seema Verma.
Other Cabinet secretaries -- including EPA head Scott Pruitt and Interior Secretary Ryan Zinke -- have come under similar scrutiny after their private flights were disclosed.
Speaking in Washington on Friday, Zinke called the brewing controversy over Cabinet secretaries flying private jets "a little BS" and said he intends to continue flying on private charter plans when the situation dictates and taxpayer dollars can be used "wisely and ethically."
Current and former senior administration officials describe a lengthy process for approving travel by secretaries and their deputies, particularly when outsize expenses like chartering an aircraft are required.
Within individual agencies, travel by Senate-confirmed officials requires signoff by legal teams and ethics officers, who vet the itinerary for conflicts. Top aides in the secretaries' personal offices, typically a deputy chief of staff or higher, make a final call.
Trips are coordinated with the White House's Office of Cabinet Affairs, though specific details like using a private plane versus a commercial airline aren't typically included in agencies' reports to their West Wing liaison.
This week, Trump's press secretary Sarah Sanders indicated the White House was considering assuming greater oversight on agency travel.
"The White House does not have a role on the front end of approving private charter flights at agencies, and that's something that we're certainly looking into from this point forward," Sanders told reporters on Thursday.
A former government official with insight into the travel review process said White House aides often scrutinize agency reports for evidence of waste or extra spending. If there appear to be strange or complex itineraries, staffers would inquire with agency officials about whether a private plane is being used.
The itineraries in question now, however, wouldn't likely have raised red flags for White House staffers because outwardly many of them did not appear to require the types of private charter flights that were ultimately used.
White House knowledge?
In some instances, Trump's senior counselor Kellyanne Conway flew aboard the private planes with Price. She said Friday she was simply traveling where she was needed and did not raise questions about the propriety of traveling on a private jet.
"I go on behalf of the White House. I have traveled with Secretary Price and Gov. (Chris) Christie, (Veterans Affairs Secretary David) Shulkin for my mission as the point person in the White House on opioids," Conway said. She said the trips were "100% business."
"Never stayed in a hotel," she said, "never even went into a restaurant."
Former health secretaries say their default was to fly on commercial aircraft. An official who worked in the agency under President Barack Obama's last HHS boss, Sylvia Mathews Burwell, said the secretary's travel was coordinated by staffers in Washington and at satellite offices around the country; once an outline for the trip emerged, advance teams and a travel authorization staffer would coordinate to book travel arrangements.
Traveling on military aircraft -- as it was revealed Price did on two occasions for trips abroad -- presents a different process.
The international travel involved itineraries in Asia and West Africa, which was approved by the White House, according to senior administration officials.
"Use of military aircraft for Cabinet and other essential travelers is sometimes an appropriate and necessary use of resources," said Raj Shah, a White House spokesman. "The White House reviews requests for military air travel closely and has limited support missions to travel that is central to the White House's mission, such as for international trips and travel for which military air is necessary and appropriate."
That approval process for flying on military aircraft involves submitting plans and itineraries to the Defense Department and the White House Military Office, according to multiple current and former administration officials. Final White House signoff comes from the deputy chief of staff for operations. A senior administration official confirms Joe Hagin, currently serving in that role, signed off for these trips.
Hagin met with agency officials earlier this year to brief them on the process for requesting military transport and give them a rundown of what types of travel should be approved.
The need for a White House signoff began under Obama, and the Trump administration has been following the same procedures.
Between January 20 and September 19, the Trump White House has authorized 77 support missions, or government flights, for Cabinet officials. In the same span in 2009, the Obama administration approved 94. The bulk of these flights is for national security officials like the secretary of state or the defense secretary, an administration official said.