Simple, but it seems unlikely, and it is also the scenario that the government would be mostly likely to be up front about sharing.

The article does not state that.

> Mr Verma's message was picked up by the UK security services who flagged it to Spanish authorities while the easyJet plane was still in the air.

> A court in Madrid heard it was assumed the message triggered alarm bells after being picked up via Gatwick's Wi-Fi network.

Gatwick is an airport, not an airline.

The article states that the Spanish courts assumed his message was intercepted in the airport, not over the in-flight wifi.

It’s complete speculation anyway. As others have pointed out, the likely route the message took to the British intelligence services is via Snapchat disclosing it directly, not through some edge-network magic TLS-breaking packet sniffer.

> after being picked up via Gatwick's Wi-Fi network.

...

>it was assumed

They don't actually state that was how the message was acquired. Snapchat uses TLS to deliver messages, so how would it be "picked up" via Wi-Fi?