An Airborne Papal Press Conference As Francis Returns Home

Pope Francis waves to the crowd at Philadelphia International Airport before departing for Rome on Sunday evening.

Laurence Kesterson/AP

About half an hour after takeoff from Philadelphia and a grueling, nine-day visit to Cuba and the United States, Pope Francis looked tired Sunday night when he appeared before reporters. He suffers from sciatica, and it was visible this week that he was having difficulty walking up stairs and standing for a long time.

Nevertheless, he took questions for close to an hour.

The pope was asked about an issue that had angered victims of clerical sex abuse: Why did he choose to show strong compassion for American bishops in one of his first speeches in the U.S.?

Francis replied that his words of comfort for bishops were not aimed at playing down the scandal but at acknowledging that many innocent clergy had also suffered because of it. It was, said the pope, a great tribulation.

Reporters asked the pope about clergy sex abuse, peace in Colombia, his impressions of the U.S. and other issues on Sunday's flight back to Rome.

Sylvia Poggoli/NPR

Abuses occur everywhere, he said, in the family and schools. But Francis added that it's much worse when the predator is a priest, "because the priest's vocation is to help the child grow toward the love of God, toward maturity. Instead, the victim is squashed by evil, and this is nearly a sacrilege."

Speaking of cover-ups of clerical abuse of minors, Francis said for the first time, specifically, that even some bishops are guilty.

Questioned about peace talks in Colombia, the pope said he was pleased when he heard that a tentative agreement had been reached last week between the government and the rebel group known as the Revolutionary Armed Forces of Colombia, or FARC. "I was very happy and felt like I was part of it," he said.

As for the refugee crisis sweeping much of Europe, Francis said the construction of barriers — like the one Hungary built along the Serbian border — to stop the influx is useless. "All walls collapse," he said, "today or tomorrow or in 100 years. Walls are not the solution. The problem remains, and with it, more hatred."

The pope was also asked what he thought about government employees who refuse — as a matter of freedom of conscience — to carry out their duties, such as issuing same-sex-marriage licenses.

The pope made no reference to the case of Kim Davis, a county clerk in Kentucky who went to jail earlier this month for refusing to issue a license to a same-sex couple. But he spoke firmly about the principle.

"Freedom of conscience is a human right," said Francis. "If a person does not allow you to be a conscientious objector, that person denies a right. Freedom of conscience must be respected in every judicial structure."

And asked what had impressed him about the United States, Francis said it was the warm, beautiful welcome he received — although it was different in each of the three cities he visited.

"Washington, a warm welcome but a little formal," he said. "New York City, a bit exuberant. Philadelphia, very demonstrative."

Before returning home to the Vatican Monday morning, as has become his custom before and after traveling Francis went to the basilica of St. Mary Major in Rome. He went to offer prayers of gratitude for his successful visit to Cuba and the United States — where he was given rock star treatment in the media and by the huge crowds that flocked to his Masses.