Cheap airline flights to Europe? They were scheduled to begin Thursday night after Great Britain granted People Express Airlines permission to offer $149 one-way flights to London. Britain had threatened to withhold the London landing rights unless the US took steps to stop antimonopoly actions stemming from the failure of Laker Airways. Liquidators for Laker have sued British Air, British Caledonian, and other airlines for conspiring to put Sir Freddie Laker out of business. But Britain decided to let People Express begin its flights, although officials said the Laker issue had not yet been resolved in US-British meetings.