This sequel is clearly aimed at kids and even sillier than the original (reviewed elsewhere on this blog) and without the previous film's novelty and much of its charm, and it makes even less sense.
There are two saving graces. First, there are some comic bits that are genuinely funny, especially Ben Stiller’s encounter early on with a self-important young Smithsonian security guard. Maybe it’s just me, but it cracked me up. Then there’s Amy Adams as Amelia Earhart. I don’t know enough about the real Earhart to judge the accuracy of the portrayal, but I also don’t care, because to the extent the original differs from the movie version, so much the worse for the original. Amy Adams would be perfect to play a grown-up Margaret Dashwood from the Emma Thompson's adaptation of Sense and Sensibility (reviewed here). And her flying suit is quite nicely form-fitting.
(A complaint in passing: The script has Amelia Earhardt refer to eyes as "cheaters," which makes no sense. As the 1938 song "Jeepers Creepers" suggests (video here), eyes in the slang of the period "cheaters" were eyeglasses. See also the 1920s slang vocabularies here and here.)