About half of the US 30 busiest airports provide Wi-Fi in public areas, according to a USA Today survey. All offer it in airline clubs. Wi-Fi use at airports continues to soar. The number of Wi-Fi connections at Dallas/Fort Worth, for instance, runs about 18,000 a month, compared with a scant 50 a month when it was new in 2000. T-Mobile has seen more than a 150% increase in its airport traffic year over year. The average time spent on T-Mobile airport connections is 40 minutes, up from about 30 minutes last year.