A new footbridge will be built airside, to allow easy transfer between terminals C and D which are both operated by the airline.
The expansions and renovations will cost around $160 million and create hundreds of new jobs.
In addition to this, Delta is increasing the number of daily flights it operates out of the airport by 100, taking the total to 260, and operating to 60 destinations. Last month, Delta added service from LaGuardia to new business markets, including Dallas/Ft. Worth; Miami; Washington-Dulles; Syracuse, N.Y.; Buffalo, N.Y.; Rochester, N.Y.; Richmond, Va.; Norfolk, Va.; Manchester, N.H.; Burlington, Vt.; Greensboro, N.C., and Louisville, Ky.
It will also be using larger aircraft on some routes, allowing increased capacity and bumping up the numbers at La Guardia.