Originally Posted by
Often1
This is all about your risk tolerance. Nobody here can predict what will happen with your inbound flight on the day of travel. If it is delayed and you no show for your onwards ticket, you will either be required to purchase a new one at walk up prices or hope that some agent is merciful.
Typically an offline I-D connection at ATL would be 90 minutes. As a rule of thumb, I would allow 3x that or 4-1/2 hours.
Well, AA does have an informal "flat-tire" rule, so that if the OP were to miss his ticketed AA flight by an hour or two, he would likely be re-accommodated -- at no additional cost -- on AA's next
available ATL-DCA flight. The problem, of course, is that the next available flight will not necessarily be on the same day!
And if the OP's LH flight were substantially delayed due to mechanical or personnel issues, he would be entitled to EC 261/2004 compensation -- which could go a long way to offsetting the cost of a last-minute ticket on a different carrier.