The chief executive said the airline has introduced “a number of measures” to avoid a repeat of the chaos seen during the Easter and jubilee periods, when thousands of flights were cancelled. The summer holidays for most schools in England and Wales start this week.
Schedule reductions across the airline industry will “help” but factors “outside our control” could affect flights, Mr Lundgren warned.
In an interview with the PA news agency at Farnborough Air Show in Hampshire, Mr Lundgren said: “We’re operating up to 1,700 flights a day.
“We’re doing it with the level of operational performance that you would have seen in 2019.
“But having said that, we can’t guarantee that there won’t be things that sit outside our control that could affect our customers, as they will affect any other airlines’ customers as well.
“We are absolutely focused on this. This is the key priority for us apart from the overriding objective to deliver safe operation.”
Mr Lundgren said one of the key risks to reliability is air traffic control providers imposing restrictions.
“It only takes one or two people in the tower to be sick and then you have flow restrictions coming into play,” he said.
“Flow restrictions could ultimately lead to cancellations.”
Asked if he is concerned some passengers could switch to Ryanair, which has not cancelled as many flights in recent months, Mr Lundgren replied: “Every airline has had cancellations.
“We deeply apologise for those events that took place when we had day-on-day challenges.
“But we’ve taken the right actions in order to correct that, and hope to continue to deliver a great operation for the rest of the summer.”