South Coast commuters will gain more than 200 additional train services a week but lose their direct airport interchange and face longer journeys under the biggest overhaul of the line's timetable in more than a decade.
The changes, taking effect on November 15, will increase peak services between Wollongong and Sydney from three to four trains an hour.
Off-peak and weekend services will double to every 30 minutes on average.
But South Coast trains will bypass Wolli Creek, where passengers currently change for Sydney Airport, and terminate at Central instead of continuing through the CBD to Bondi Junction.
The overhaul separates South Coast intercity trains from T4 suburban services between Arncliffe and Central, allowing them to use different tracks.
The NSW government says this will reduce bottlenecks and improve reliability.
The decision creates a trade-off for airport passengers: change twice, at Sutherland or Hurstville and then Wolli Creek, or remain on board to Central and catch an airport train back out of the city.
Trains between Wollongong and Sydney will run every 15 minutes in peak periods and every half-hour on average off-peak and on weekends from November 15. (ABC Illawarra: Rory Macdonald)
Sydney Trains chief executive Matt Longland acknowledged the inconvenience.
"Certainly we do appreciate that this will involve changes for passengers that need to access the airport," he said.
Mr Longland said about two per cent of South Coast passengers used the airport connection, but recognised its importance to those travellers.
He said the problem involved the station's layout, as only two of the four Illawarra tracks through Wolli Creek have platforms.
The express tracks allocated to South Coast services do not.
"For any elderly passengers or anybody with needs or large luggage, my recommendation would be Central may be a better option to change," Mr Longland said.
He pointed to staff assistance, lifts and more frequent airport services at Central.
All Sydney-bound South Coast trains will stop at Sydenham, giving passengers a Metro connection to Chatswood, Macquarie Park and Sydney's north-west.
The interchange will also provide access towards Bankstown once the south-west Metro extension opens, although the timetable announcement does not confirm an opening date.
Wollongong station will have four Sydney-bound trains an hour during peak periods under the new timetable. (ABC Illawarra: Nick McLaren)
Additional services will operate between Thirroul and Wollongong, including a shuttle every 15 minutes between 8am and 9am.
The government says some journeys will take longer because of revised stopping patterns.
Passengers will also need to adjust to different departure times and connections.
The changes support the rollout of Mariyung trains on the South Coast, bringing improved accessibility, charging ports and luggage space.