Thanks for the replies, guys.

I checked the alierons before flight, and they were fine. Moreover, I did not apply any alieron once the plane took off. I suspect it was the wind, but the fact that the servos came loose probably meant I could not control it even if I had wanted to.

I think the fact that my engine is slightly pointed upwards doesn't help matters. It could be that the plane got off too fast, took the wind under the right wing, and flipped it over.

The investigation continues. [:-]