According to FlightRadar24, IB6011 has as an assigned aircraft EC-MKI, that is coming back from Montevideo and is planning to land at 5.54am - so even if it is still showing "on time", it seems it will be delayed to more or less the time IB has told you. Still, double check with IB staff on MAD because they may be able to pull a last minute change of equipment and the flight may leave nearly on-time or with a much shorter delay.