The right time at blore cant is around 800-15 and generally its late by around 30 mins and so is the case with garib rath as u need to be there by 10 am to catch flight by 11am and morning rush hour traffic. Better opt for cape bangalore island exp which reaches by 700 730 or prefer ksrtc bus frm kottayam or erkm airawat club class get down at shanthinagar bus station there u can get airport volvo vajra service with 15 min interval which take 90 min. These are two options see that in both cases train or bus u arrive by 700 even thouvh u are late by 1 hr you can make it to airport by 10am.