I am unsure as to why you would want a flight mode as tablets don't have GSM signals, flight modes turned off mobile phone broadcast and receive so as not to interfere with flight instruments but tablets don't do this anyaway. Generally more modern versions of tablets don't have a flight mode at all because it is a hang over from when tablets just used a hacked mobile phone OS, now Android on tablets is specifically for tablets there is no need for a flight mode. If you can confirm exactly what features it is you are looking for in flight mode I will do my best to help
I'm not the OP, however could I perhaps rephrase this question to cover a non-flight scenario - Can you turn off the wifi?
I do this whenever possible (i.e. when not surfing the web) for two reasons - wifi drains the battery at a faster rate (this is particularly noticable on my kindle), and I consider wifi radiation to be unhealthy (I'm not intending to get into a discussion or argument about this however)
From the initial response I inferred this wasn't possible, however it would be good to have definitive confiirmation. This would be a deal breaker for me.