The Flight of Flamingo by Elizabeth Darrell
Set between the years 1920 and 1945, this is the saga of the Kirkland family, the manufacturers of the first flying boat. Leone Kirkland, who inherits the business from her father, finds herself caught in the middle of a family feud involving her lover, which will only be resolved by World War II. Elizabeth Darrell has also written "The Jade Alliance", "The Gathering Wolves", "At the Going Down of the Sun" and "And in the Morning".