'The Last Flight of Noah's Ark' is average.
One of the reasons for that is the lacklustre plot, which is one we've practically already seen before from Disney in years prior - like 1960's 'Swiss Family Robinson' and 1966's 'Lt. Robin Crusoe U.S.N.'. This isn't incredibly similar to those two, but they are certainly in the same ballpark.
The premise doesn't have much about it in terms of action or heart, the ending threatens to finish with a highly meaningful moment but instead bottles it in favour of a more happier conclusion. Elsewhere, you have a forgettable cast. Elliott Gould (Dugan) and Geneviève Bujold (Bernadette) are alright, though they lack the necessary chemistry together.
Close to being a good'un, but just misses out in my books.