Ghengis is as usual, spot on; but why turn your nose up at Maintenance?
The field is bigger than you think and most airlines have Technical Services sections (or departments) employing graduate engineers on development work. The bigger the airline, the more opportunities there are - at one time British Airways even employed Metallurgists. One structures engineer that worked in our section left aircraft manfacture because he was sick of designing emergency exit hatches. He designed the original, modified it for the freight version, developed it to overcome in-service difficulties - you get the picture. In an airline 'maintenance' office he works on structural repairs and modifications covering the whole aircraft.
The point is, designers tend to end up specialised in small areas. (Lu Zuckerman being an obvious exception - some advice for this young chap please...) whereas airline engineering departments cover all the operating issues.