(Reuters) – Strikes and staff shortages are forcing airlines to cancel thousands of flights and causing hours-long queues at major airports, dashing hopes of a sizzling first summer after COVID lockdowns. Here is a summary of some of the key developments: LABOUR UNREST: After sweeping job cuts and pay cuts when COVID-19 brought travel to a grinding halt, staff across the industry from pilots to baggage handlers are asking for big pay increases and better working conditions. Norwegian Air in June agreed a 3.7% pay rise for pilots among other benefits, in a sign of what other airlines may have t…