Will there be more air travel chaos this summer?

Nats is far from the only organisation focussing on resilience.

It's a big theme for airlines like EasyJet, one of Europe's largest. The summer peak is already here and the low-cost carrier is taking about 310,000 passengers on more than 1,900 flights each day. Its planes complete an average of eight flights per day and as many as 325 of them can be in the sky at a time.

If anything happens to leave aircraft and crews in the wrong place, the volume and complexity of the packed international schedule means disruption can quickly build up.

EasyJet's operations are co-ordinated from its new expanded "Integrated Control Centre" in Luton.

With the runway and air traffic control tower of nearby Luton Airport visible in the distance, I spoke to the airline's Director of Network Control, Gill Baudot.

She said the business spends most of the winter learning from the previous summer. Measures EasyJet has focussed on include having enough standby crew available.

It has also built "firebreaks" into its programme. This means longer turnaround times than the usual 35 minutes on longer flights, Ms Baudot says, "so we've got more time to pick up from any issues... so we can get more of our aircraft away on time." Otherwise, "once you start of go off schedule it's really hard to bring it back".

The airline says it now has 14 standby aircraft across its network.

If a plane gets delayed early on, rather than letting delays accumulate over the day, a spare aircraft and crew can be "injected" to take on the second half of the programme.

Ms Baudot says that makes a huge difference, "because then you're not over-running into the following day, you're not ending up with very last-minute overnight delays or last minute cancellations".

Post-Brexit rules are an additional complication, as UK and EU crews can't operate interchangeably.

If flights have to be cancelled, the airline can see which ones have the most vulnerable customers or children on board, and try to prioritise.