Pellegrino, Charles. Flying to Valhalla
Divergence: 1912 CE
What if: The Titanic did not sink, which led to aviator Harriet Quimby living an extra 40 years.
Summary: First-contact tale set in 2054, but a digression on pp. 178-179 reveals that it's not quite set in our future.
Published: Morrow 1993 (0688125069); SFBC 1993; Avon/AvoNova 1994 (0380718812).