If you are with a tour company, they should be able to keep you updated before you either leave your hotel or arrive at the airport as to whether there is a delay.
If you are not with a tour company you can ask the hotel reception staff to check for you, or look on the internet and website for the flight operator, then under 'timetable' or 'arrivals'.
Not in a hotel: You can always try and contact the TUI Office on Sal or Thomas Cook who are based in the office of 'Travel Solutions' before you go to the airport or, look online for flight departure updates.
On Sal at Amilcar Cabral Airport, once you have checked in and you have enough time, you don't have to go immediately through Passport Control, you can go back into the foyer area and use the shops or cafe or the small snack bar on the first level (however read next paragraph). There aren't any 'meals' served in the snack bar on the other side of Passport Control (in Duty Free area), just sandwiches or pizza slices and one or two other items but they are a bit more expensive than the restaurant in the outside foyer, so you may want to eat before going through, or at least get yourself a takeaway sandwich to take through Passport Control to Duty Free and waiting area. It could be a long and boring wait if the flight is delayed. There is only the one snack bar inside the Duty Free area.
Be thoughtful though, as now there are more flights departing Sal, more people will need to be processed at check in, so long queue's could suddenly appear at Check in (for luggage drop off) if more buses have arrived and dropped off more tourists for their flights back to other countries while you are out in the foyer cafe ordering and waiting for a meal, so long queues can appear at Security and Passport Control when you get back and you could find your self at the end of each queue. So on saying you don't need to go through security and passport control immediately to go and get a meal or a cheaper sandwich in the foyer, may cause you delays in getting through into Duty Free and, I wouldn't want people worrying that they could miss their flight!
If the flight is going to be delayed, check with Airport Staff as to what the expected time is of arrival. In general circumstances (pre 2012), you must go through Passport Control a minimum of 1hr before the flight is due to depart, check if this is still the case even if the flight is delayed!
I am aware that tour operators have kept people at the hotels if they are aware that there is going to be a long delay.
If you have children it may be best to get some drinks and snacks or make some sandwiches to take to the airport. There are a number of Chinese shops in Santa Maria where you can buy drinks, sweets and food items like crisps or snacks or you can just visit Cazu Supermercado, its a mini market that most residents use in Santa Maria. All the taxi drivers will know where it is.
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