Dragonsword Series by Gael Baudino

Transported to a land that cannot exist, transformed from Suzanne and Braithwaite into Alouzon and Dythragor, they are the bearers of the Dragonswords, guardians of Gryylth and defenders of the Circle. They are the dragonmasters.

Wings of Doom were spreading destruction across the kingdom of Gryylth. Twentieth-century weapons were raining down upon an unsuspecting land where sharpened blades and pointed spears had always been the only true warrior's tools. And for Suzanne Helling, UCLA teacher of medieval studies, the call of the dragon Silbakor has suddenly come again, transforming her into Alouzon Dragonmaster, Guardian of the land... moreWings of Doom were spreading destruction across the kingdom of Gryylth. Twentieth-century weapons were raining down upon an unsuspecting land where sharpened blades and pointed spears had always been the only true warrior's tools. And for Suzanne Helling, UCLA teacher of medieval studies, the call of the dragon Silbakor has suddenly come again, transforming her into Alouzon Dragonmaster, Guardian of the land. But even as Silbakor prepares to return Suzanne to Gryylth, they are attacked by another dragon with enough power to rival Silbakor himself. This creature of evil was ready to pursue them all the way from Los Angeles to the very heart of Gryylth. And once returned to this land originally conjured by the imagination of a now dead professor, can Suzanne find and defeat this nameless, faceless enemy? less

The final volume in Baudino's powerful trilogy tells of a young woman who's transported to an alternate realm to defend its people. Suzanne sets out to stop the flying things that are destroying Gryylth, even though Suzanne was responsible for bringing the fighter jets to Gryylth in the first place.