(ShareCast News) - Budget airline easyJet's passenger numbers and load factor improved in December.The FTSE 100 company's passenger numbers jumped 15.1% to 5.57m last month, compared to the same month the previous year.Meanwhile the load factor - the number of passengers as a proportion of the number of seats available - rose 3.3 percentage points to 89.9%.On a rolling basis, passenger numbers rose 6.6% to 74.45m and the load factor was largely flat at 91.5%.The company defines passengers as the "number of earned seats flown", including seats that are flown whether or not the passenger turns up as easyJet is a no-refund airline.