Im not sure if this has been discussed before but I recently tried to buy a plane which looked like a real bargain but was informed I could not, as it belonged to an Alliance member and was set below the market value.
This seems ludicrous to me, I understand completely why such a rule is in place and think its wise. To have a complete blanket ban though seems overly harsh, if a member has a plane on the open market at a set price, why can an alliance member not buy it, IF its obviously not a set up money shifting/ gifting operation.
A perfect solution for cases like this, would be to allow alliance members to buy any aircraft, set at a below market rate, from an alliance member after it had been on the open market for a set period of time (2 weeks) which would allow other players to take up the offer if they fancied it. If its still not sold at this point and the price has not been altered, then alliance members could also then purchase it.
Its a small thing but something I think should be addressed, when I clicked to buy the plan I had no idea it was even on sale from an alliance member, he/she could not get the price he/she wanted and I could not buy an aircraft at a very competitive price. Anti cheating measures are good and required, they need to be set up wisely though or otherwise restrict the game too much