Lomas moves into the chair-elect role until she takes up the position in 2012, when existing chairman Jamie Hindhaugh will become immediate past chair.
Prior to Omnicom Group, she has worked for American Express and American Airlines.
Hindhaugh, who is BBC head of production London 2012 and head of sourcing - logistics, became chair in January this year.
He will move from the role to concentrate on the BBC’s production for the Olympics.
Lomas said: "Being appointed is a real honour for me and a chance to give something back to the industry. I plan to support Jamie and help to take all the good work that’s been done so far and consolidate it to ensure ITM members can continue to demonstrate the value of their roles to their businesses."
Buyer and supplier partnerships, the development of industry qualifications and understanding the role of the ITM regions will be the focus for Lomas, as well as helping buyers to highlight the value of managed travel to clients.