The Boeing family of new generation 737 aircraft would allow for fleet
consistency however, prices and more importantly, financing was prohibitive.
Airbus has a competitive aircraft in the 318/219/320/321 albeit not
consistent with present fleet configuration.
Essentially, the deciding factor is price and financing. In an effort to
secure the aircraft contract, Airbus offered some attractive financing that
Boeing wasn't unwilling to match.
As TWA has now been purchased by American Airlines, the Airbus aircraft
contract has been cancelled since that aircraft doesn't fit American's fleet
I recieved this as an email from a TWA Employee. This should answer all questions.