Like every journalist who has ever been on a trip with the pope on board Shepherd One, as his plane is known, I am in no doubt as to the significance of the in-flight press conference. Being part of the Vatican press entourage means you're up close to the pontiff, but you hardly ever get an unscripted quote – even Francis is very carefully handled by media managers.
But the traditional papal press conference in the clouds is a rare chance for him to speak off the cuff, and yesterday he did. "A priest who has sex with a child betrays God," he told assembled journalists. "A priest needs to lead children to sanctity, and children trust him. But instead he abuses them, and this is terrible. I compare it to a satanic mass."
This last comparison is significant. While Pope Francis is a man of gestures, he knows there are some issues on which words really count, and none more so than the vexed, and continuing, issue of child abuse.
The former Argentinian cardinal spelled it out in a way all clerics – however far from Rome and however out of touch with the current clean-up operation – will understand. No Catholic priest in his right mind would think of officiating at a satanic mass, a ritual that inverts the worship of God to pay homage instead to the devil. Satanic masses have their roots in medieval times, and have historically been a way of both ridiculing and undermining the authority of the church. They are also the biggest shock tactic imaginable to any Catholic cleric: they are diametrically opposed to everything the church stands for: the ultimate evil.
It is still, of course, strange indeed that any priest would think that performing a satanic mass is worse than committing child abuse, or that it's worse than covering up when another priest has committed child abuse. But, weird though it sounds, priests with that mindset do exist in the Catholic church, even in the 21st century. So although he was talking to journalists on his flight home from the Middle East, Pope Francis was really speaking to the ordained men he leads – and in the clearest possible terms, with a comparison any one of them could understand. There is no excuse any more, he was saying. Don't think you are ever, in any circumstances, protecting the church by covering up these crimes, because you aren't. "A priest who does this betrays the body of the Lord," he said.
These words show that Pope Francis means to tackle the paedophilia problem head-on. It won't be easy, and he must know that better than anyone – as the UN said in a report on the Vatican's handling of the crisis, preserving the church's reputation has been placed above the protection of children, time and again, over recent years. The attitude the UN identified is systemic: it is ingrained into many clerics that cover-ups are better than admissions of guilt for the church, and it is that mindset that Francis has to change.
Any priest who betrays the body of the Lord, like any priest who performs a satanic mass, isn't really a priest at all. As Francis said, the time has come for zero tolerance.
His wider reforms are, slowly, beginning to change the Catholic church, and in the long term there is much to hope for. But nothing is really possible until the cancer of paedophilia within it has been properly excised. Francis has picked up his scalpel and shown he means business. We all have to hope now that the operation – which won't be easy – is a success.