Does the training set of one topic will be useful to predicate the sentiment for any other topic?
Since you have trained your model on air-line tweets, the model will learn the characteristics of the air-line tweets. There could be words used in air-line tweets which are positive and contain great weightage but never even used in other tweets leading to negative results. 
I suggest you to try 


Get a dataset which contains all kinds of tweets which you desire essentially similar to what your task ahead is.
Look into Transfer learning.