If your T.C. flight has been sub-contracted to Free Bird, you can go online to the Free Bird website and book seats together etc., Something that T.C. should tell you on their website. I emailed them last week as there is no facility on their website to pre book seats and last May we got to the Airport 3 1.2 early to get seats. I have had no reply from T.C.
So website details
https://secure.paxport.net/freebirdairlines/login/wicket:pageMapName/wicket-0If you do go online to book put your flight number with no spaces.