Shares in Easyjet ascended on Tuesday after the British budget airline said it now expects an increase in revenues per seat in the first half.The company said revenue per seat at constant currency should rise by 2% on last year, compared with its previous guidance of "flat to very slightly up".Seats flown increased by 2.9% year-on-year to 16.6m in the first quarter ended 31 December 2014, while passengers carried rose 4.1% to 14.9m. The load factor, a measure of how full its planes are, improved by one percentage point over the prior year to 89.7%.Revenues for the three-month period rose 3.8% year-on-year to £931m, while revenue per seat increased by 0.8% to £56.16, a 3.7% improvement at constant currency."Easyjet has made a good start to the year by continuing to deliver its strategy of making travel easy and affordable for passengers," said chief executive Carolyn McCall."We enjoyed a strong October across the network - particularly on UK leisure flights to beach destinations and on French domestic routes where we continued to build passenger numbers after a busy September."Easyjet said it expects to report a loss before tax of £10m-30m in the first half, compared with a £53m loss the year before.The company said its jet fuel bill in the first half would be £30m-35m less than last year and fuel costs over the whole year ending 30 September 2015 would be £90m-130m lower."Easyjet expects that lower fuel costs will be beneficial for its customers as fares adjust."The stock was up 4.5% at 1,835p by 08:42.