Starting Monday, the Metropolitan Transit Authority will roll out a fleet of vintage buses along the M42 crosstown line.

The fleet will include models used in the city from 1949 to 1984 including the first General Motors bus with air-conditioning.

Nostalgic straphangers and curious riders can use their MetroCards on the throwback rides.

Buses will depart from 42nd Street and 12th Avenue at 8:30 am, 11:30 a.m., and 2:30 p.m. Monday through Friday.

They will also be on display for free at Union Square and at 6th Avenue and 35th Street.