* Warns of prolonged revenue hit from pandemic * launches 475 mln stg rights issue * Shares down 3.4% in early trading (Adds share move, analyst comments, details from statement) March 17 (Reuters) - Snack food firm SSP asked shareholders for 475 million pounds ($661 million) on Wednesday, warning it might take until 2024 for commuters to return to chains such as Upper Crust and Caffè Ritazza in the same numbers as before the pandemic. “The impact of the pandemic on working practices may have a longer term impact on both business travel in Air and commuter travel in Rail,” said SSP, which has already cut 14,000 jobs. The London-based firm, whose chains sell food and drinks in airports and train stations in 35 countries, said conditions did not improve in the first two quarters of 2020-2021 fiscal year. The fully underwritten 12 for 25 rights issue of 258.1 million shares is priced at 184 pence per new share, about 47% below Tuesday’s closing price of 345.8 pence. SSP shares were down 3.4% to 334 pence at 0850 GMT, deepening a slide that has wiped out roughly half - about 1.8 billion pounds - of its market value since February 2020. SSP raised 216 million pounds in a share sale last March to help cope with the pandemic, which forced people to work from home and brought leisure trips to a halt. At the peak of the crisis, it shut about 2,500 outlets and furloughed over 22,000 employees across the world. Its 2019 annual report showed it had 39,549 staff globally. SSP also announced on Wednesday a two-year extension to its bank facilities due to mature in 2022 and waivers of existing borrowing terms. The company, which also runs Burger King chains in airports and train stations across the UK, Belgium, Egypt, China and Hong Kong, has a portfolio of over 550 brands, including upmarket restaurants such as Le Train Blue in Paris. It said it had burned through 120.1 million pounds of cash in the four months to Jan. 31, with 420 million pounds in available liquidity at the end of the period. “We harbour some concerns about the lasting impact of remote working on recovered air and rail passenger volumes,” Stifel analysts said in a note.