It's probably the VIP Select service they are using. Here's a description I found about the program:

"Delta Introduces VIP Select™
Delta VIP Select offers personalized one-on-one assistance through the airport. The service is available for travel at New York JFK, Los Angeles and San Francisco for a fee of US$125 per airport meet for one person or US$200 for two people. The service includes meeting the traveller curbside and/or at the arrival gate; assisting with baggage, porter service and check-in; accompanying the traveller through baggage drop, check-in and security; complimentary access to the Delta Sky Club®; and boarding the traveller discretely at their preferred time. (Source: Delta Air Lines, January 2012)"