My main problem with the movie

It's not really like that though is it? It's not as if it switched genres, or the tone drastically changed like the example you've given. It was always a thriller about a kidnapping and Russell's character trying to convince people she's missing was one part of the plot.

While I agree I prefer the first part to the second, which becomes a bit more actiony, I still enjoy the movie, and for the record like it more than Flightplan.

It's an above average kidnapping movie with an outstanding performance by Walsh who is absolutely menacing and one of Gainey's better performances although he's always good. Russell does the Everyman very well while being convincingly capable to rescue his wife without going Rambo. I think it's a matter of it wasn't what you expected and to be honest a movie like you describe with Russell running around for 90 minutes trying to convince authorities his wife was kidnapped sounds very boring.

In fact I agree with much of what you said.
I am also thought they quickly drop the suspension part about the bad guys identity and the fate of his wife. In my opinion the magic of the first part stems from the fact that each of us can feel the anxiety, confusion, helplessness of the main protagonist looking for his wife. The movie is top class for kidnapping movie but could have been better.