I would always recommend removing the default Yii URL rules and add your own, specific ones. Also try using useStrictParsing. Both of these help to control your URLs more closely and will generate 404s as appropriate.
This would be my approach:
'urlManager'=>array(
'showScriptName' => false,
'urlFormat'=>'path',
'useStrictParsing'=>true,
'rules'=>array(
'services/airline-search/<trip:round-trip|one-way>/<origin:\w+>' => 'airlineSearch/roundTripSearch',
),
),
And then in your controller:
<?php
class AirlineSearchController extends Controller
{
public function actionRoundTripSearch($origin)
{
print_r($_GET); // Array ( [trip] => round-trip [origin] => delhi )
// Use the full route as first param 'airlineSearch/roundTripSearch'
// This may have been the cause of your issue
echo $this->createUrl('airlineSearch/roundTripSearch',array('trip' => 'round-trip', 'origin'=>'delhi'));
// echoes /services/airline-search/round-trip/delhi
}
public function actionLets()
{
}
?>