chief executive michael o'leary made the vow to a french newspaper .
he attributed the cuts to lower oil prices and said savings will be passed on .
the controversial boss said ryanair 's average ticket price could drop by £ 4 .
new boeing planes ordered by irish carrier will have more capacity .
mr o'leary also took aim at air france and predicted more troubles times .
he disputed claims that ryanair staff face poor conditions and wages .