Most of Swiss Air's flights between its Zurich hub and its 'second city,' Geneva, are being replaced by 'air train' service between the two cities. The change, prompted by the Covid falloff in air travel, may become permanent, in part for environmental benefits.
Before the pandemic, there were up to ten flights a day between the two cities, with most passengers either headed to international destinations via Zurich, the airline's only international hub, or returning from there to Geneva.
Since Swiss began service after lockdown, two to four flights a day have been more than enough to handle the passenger numbers, but have not made good connections with all overseas flights. So Swiss has arranged for up to ten 'air trains' a day. Operated by the Swiss Railroads, many are regular trains whose fare is included in the flight price.
Air train service is also being extended to Basel and Lugano airports. The rail time between Geneva and Zurich is nearly three hours compared to 35 minutes by air, but the usual advantages of rail vs getting to airports will cover some of that. Zurich and Basel are close enough that no regular air service existed.