What factors led British Airways to transition from Terminal 5 to Terminal 3 at O'Hare Airport?

Big changes are taking off at ORD Airport, where British Airways is saying cheerio to Chicago O'Hare Airport Terminal 5 for departures and hello to Terminal 3. Starting April 25, passengers flying with the UK's flagship carrier to destinations across the pond will begin their journey from the revamped digs of Terminal 3, a switch aimed at boosting convenience for these globetrotters.