My Heart Has Wings — Elizabeth Hoy

Jan's busy life was one long rush; a full day's office work for a most exacting boss (a brilliant but temperamental aircraft designer), then housekeeping for her father, sister and brother, on a frighteningly inadequate income, in their inconvenient but much-loved home. Even the long journey to and from work had to be spent usefully in knitting. But still her thoughts found time to stray far, far into the sky, where a certain test pilot carried out his thrilling, dangerous missions....

Not that Jan imagined that Mike would ever give her a serious thought. Everybody knew that he was attached to Erica Scott-Manly, daughter of the head of the firm; Erica, who was beautiful and clever and rich, and, maddeningly, quite unspoiled by all the gifts with which Fortune had surrounded her. So how could there be any chance for a quiet, unremarkable girl like Jan? But all that didn't stop her thinking and dreaming about him.