Major European rail hubs like Gard Du Nord in Paris are also seeing a huge surge in traffic where a power problem added to their issues.
Tens of thousands of half-term holidaymakers are stranded abroad after up to 200 flights were cancelled over the weekend.
Airline easyJet cancelled 80 flights on Sunday "due to the ongoing challenging environment", while Eurostar passengers faced delays and cancellations because of power supply problems near Paris.
The vast majority of cancellations from Gatwick Airport on Sunday were easyJet flights, but British Airways, Wizz Air and Vueling are also understood to have been affected.
The aviation industry is suffering from staff shortages after letting thousands of people go during the coronavirus pandemic.
Airlines are now struggling to recruit new workers and have their security checks processed, which they say are being delayed by government red tape.
Transport Secretary Grant Shapps claimed travel firms have "seriously oversold flights and holidays relative to their capacity to deliver" despite government warnings.
He has said he will "do absolutely everything possible to make sure" holidaymakers are able to get away without issues during the summer.
Following a meeting with airports, airlines and ground handling companies last week, the cabinet minister said he had answered industry demands to speed up security checks for workers and allow some staff in non-security related jobs to take up training immediately.
But he said it is up to the sector to fix the issues, accusing bosses of "cutting too far", despite receiving £8bn of state support and having access to furlough money to keep staff on the books while COVID travel restrictions were in place.
He said: "Clearly, they have been taken by surprise by the way people have returned to travel after two years of being locked down, but I'm not surprised - we were saying all along: 'You will need to be ready for this'."