There has been some reason to believe the business jet industry is pulling out of its tailspin, but Gulfstream did little to ease investor concerns in the first quarter. General Dynamics reported a book-to-bill ratio for its aerospace unit of just 0.77, down from 1.3 in the fourth quarter of 2017. Gulfstream also delayed initial deliveries of its G500 midsize jet from the current quarter to the last four months of the year.