Forcing a user to update or upgrade software (either without consent in the background or by restricting access to the software until the user performs the necessary steps) is a painful experience for all users.
Let's say that you have a user who tries to boot your software (likely with the intention of accessing flight or ticket information) and then they are greeted with a message box informing them that the app is unusable until updated. This is a sort of system that many big software companies do use, but they are often in the business of malware-protection or some other sort of software that relies on updates to operate. These sorts of companies have no choice about this solution, but it is still an overall poor experience for the user.
On the other hand, say that you have decided to save the user the hassle of having to update and instead you provide a solution which does all the updating work in the background. At first glance, this seems like a great solution, until the update contains some large changes or even fails and then damages something. People also don't like change (especially older generations), and the act of manually having to click on an update button (for example) indicates to the individual that there will be changes. But, background updates don't warn the user about any modifications to the software, and when they next plan on using the software it looks completely different and will often drive them away from using your software. You want to make the experience as easy as possible for the end user, but you do not want to take their control away.
Finally, you also have many other issues such as the fact that people in rural areas with limited access to the internet are going to find using the software next to impossible. Of course, if the software requires internet access anyway this might not be such a big problem, but there are certain people who do not want to make changes to their devices for the fear of not knowing what they're doing. As commented above, Windows 10 has recently been under scrutiny after automatic updates were conducted in the background and often actually caused serious damage to many machines globally. Not to mention, if the software is completely locally-based and does not rely on remote servers to retrieve data, you should reconsider how your application operates. You cannot have minor updates being sent out every few days - that's a recipe to lose users very quickly.
Overall, it is just poor overall experience to force users to update to minor versions of software. There is a lot of room for error, and many users will not like adjusting to new interfaces or features very quickly - especially if the changes happened without them knowing. However, the one exception to this rule is that if you need to deploy updates which fix major bugs, you need to take the right path to fix your software, but never take the control from the end-user.