French news agency AFP disclosed late Tuesday that Philippe's office had hired an Airbus A340 with first-class seats to fly from Japan to Paris on 6 December instead of using an A340 army transport plane flying the same route at roughly the same time.
The prime minister's office has argued that Philippe needed to be back in Paris urgently because President Emmanuel Macron was leaving the country and that the air force plane was too uncomfortable for a night flight.
"It's complicated to move the prime minister around and it's expensive," Philippe told RTL radio on Wednesday. "I understand both the surprise and the questions that French people are asking themselves."
Asked if it had been a mistake, he replied: "I take responsibility for this decision completely, I take responsibility to such an extent that I want to explain it."
Philippe was returning from the far-flung French Pacific territory of New Caledonia on 5 December along with a 60-strong delegation of officials and ministers.
For the first leg of the journey from Noumea to Tokyo, they used the air force plane.
But instead of continuing on board this aircraft to Paris, his office hired the private A340 to complete their journey and arrived home two hours before the army plane which landed in Paris almost empty.
"We knew that there wasn't a commercial flight at that time and that we needed to get back. We knew we needed to get back for something vital which is that the president was leaving on the Wednesday morning of our return," Philippe added.
He explained that the requirements of his job meant that moving around was expensive but that he did everything possible to keep a lid on costs.
"If you had invited Edouard Philippe, I would have come in the metro which would have cost me 1.90 or 2 euros. But... I arrived with four vehicles, motorbikes, 15 people, and a doctor and a transmitter, who stay with me because these are the resources given to a prime minister to enable him to work at all times," he added.