BOSTON--(BUSINESS WIRE)--TA Associates, a leading global growth private equity firm, today announced that it has completed an investment in Plusgrade, a leading provider of revenue solutions to the travel industry. Financial terms of the transaction were not disclosed. Founded in 2009, Plusgrade helps airlines manage and optimize revenue generated from seat upgrades and other premium services. Through the company’s proprietary software-as-a-service platform, airlines are able to capture increme