Looking to fly AA to TXL thru lhr. Is there a minimum "legal" transfer time at lhr? I would like to arrive lhr via AA 116 at 11:25 and depart on BA982 at 12:50. No booking service (starting with aa.com) includes this as a possibulity, while it's possible to go thru Helsinki or Madrid with a much shorter connection time. Is it lhr or something else?