My cell phone, can I turn it on now?

Preparing to take off, a guy around 20ieth I guess, was sitting beside me. He asked me whether or not the cell phone must be turned off. I said. you must turn it off. As my spoken Chinese was not good enough to explain how the phone signal may interrupt the navigation system, I just told him with a very simple Chinese politely. He got my point though. He eventually turned his phone off.

We started talking, from this point I knew that he came to Beijing to take a part in a car competition, now heading back to Dalian by plane because he can't get a ticket for the train due to peak season, just the same reason as mine. In a short pause, he suddenly made a comment, "Well, I think it's supposed to be OK now to turn on the phone as we have already taken off".... No, I said. I tried to explain that some plane accident might occur due to navigation failure because of signal disturbance caused by some forgetting to turn the phone off. Then, his response was just nodding his head while putting back his phone into the bag.

I was just wondering, what if there was a lot of people having the same thinking as his that turning on cell phones inside the plane was not a big deal. Hmm, good that he and I had a talk! The plane landed in Dalian Airport at 1 a.m.