Why Spirit AeroSystems Stock Just Popped 8.5%

Shares of Boeing (NYSE: BA) airplane-parts supplier Spirit AeroSystems (NYSE: SPR) stock are up a strong 8.5% in 1:55 p.m. EDT trading Thursday -- and if I had to take a guess, I'd say they're up for the same reason Boeing itself is up today: Hope that airlines are getting healthier. In a column earlier today, Barron's magazine pointed out that American Airlines saw 71% sequential growth in passengers between April and May and is planning to expand capacity on domestic flights to about 55% of "normal" by July. More airplanes flying also means, though, that more airplanes will eventually get worn out and need to be replaced.