Shares in easyJet soared to a record high today as the budget airline said annual profits will smash City forecasts with a surge of up to 50%.

The Luton-based carrier, a major operator out of Stansted, defied concerns the recent heatwave will hit last-minute getaways by saying almost three-quarter of its summer seats are booked.

Easyjet said rising passenger numbers and strong third-quarter revenues will mean pre-tax profits of up to £480million for the year to the end of September, compared with £317m a year earlier. That propelled its shares 8% higher on the FTSE 100 Index.

Revenues for its third quarter to the end of June surged 10.5% to £1.14 billion and passenger numbers increased 2.6% to 16.4m. Revenues per seat grew by 6.1% at constant currency to £61.44.

Analysts at Numis Securities had expected annual profits of about £440m and third-quarter revenues of £1.12m.

Easyjet’s shares stumbled on Tuesday after analysts at HSBC downgraded the carrier on worries the recent British heatwave would cut demand for impromptu foreign holidays, cutting its profit forecast to £433 million.

“We think demand for holiday flights will be melting as fast the ice-creams on Clacton beach in the current heatwave,” said HSBC analysts in a note.

Chief executive Carolyn McCall said 73% of its seats are now booked for its peak April to September period and annual profits will be between £450 million and £480 million unless it hits significant disruption.

She said: “EasyJet has delivered a strong performance in the third quarter in a benign capacity environment.”

Shares in the airline touched a high of 1449p in early trading, the highest level since its stock market flotation in 2000. Easyjet’s shares have continued climbing since its promotion to the FTSE 100 in March.

However, the airline’s load factor - a measure of how full its planes are - dipped to 88.2% from 89.1% a year earlier after Easter fell a week earlier on March 31.

Higher airport charges and disruption from strikes and de-icing helped push costs 4.5% higher at constant currency.

The carrier was recently given the green light to modernise its fleet after shareholders backed plans to order up to 235 new aircraft - defying objections from founder Sir Stelios Haji-Ioannou.

EasyJet will upgrade and expand its fleet by acquiring 135 Airbus planes over the next nine years. There is also an option to buy a further 100 Airbus planes as part of the deal.

The purchase is expected to allow easyJet to boost passenger numbers from the current level of 60 million a year to around 90 million.

Ricahrd Hunter, head of equities at Hargreaves Lansdown Stockbrokers, said easyJet’s success story looks set to continue.

He said: “Investor appetite for an aggressive player in a difficult market seems insatiable.”