St. Louis is preparing to offer up to 20 minutes of free wireless Internet access at Lambert, beginning Nov. 1. Travelers currently are charged $7.95 a day, and that is the rate they will continue to pay after using up their free minutes. A representative of Boingo Wireless Inc. told the St. Louis Airport Authority that only 13 of the 50 largest airports provide all-free wireless Internet access, while 16 charge for access. The remainder offer a limited free service, similar to the one Lambert plans to roll out in three months. The Airport Authority on agreed to amend its seven-year contract with Boingo, its wireless provider, to accommodate the limited free service. The move also must be approved by the St. Louis Board of Aldermen and the Board of Estimate and Apportionment.