Often, at the start of the flight, the crew will announce the times at which they'll be serving meals. Normally the meals are shortly after departure and/or shortly before landing. If you want to eat the first meal you can simply stay awake until it is served. For the final meal, the crew normally has to wake most everyone up for landing to check seatbelts, etc. so they just do it a bit earlier to do the meal service - all the lights turn on and it there is a lot of noise and people moving about in the cabin so it's hard to sleep. Many flights tend to try to match service the arrival time to help with jet lag, often the service will be as soon as possible for allow passengers who wish to sleep as long an interrupted period as possible. There is sometimes a paper menu provided at each seat with some hints about meal times like "dinner" (you can surmise what might be a reasonable time range in either the origin or destination), "pre-arrival snack", etc.

Missing mid-flight meals or snacks on long haul flights is easier than missing the services close to departure and arrival. However, the crew is normally flexible about these, the food served is typically less perishable, and you'll likely easily be able to get this snack later if you slept through the service and wake up hungry.

Some airlines have come up with a solutions to the conflict of some passengers wanting to sleep and others wanting to be woken up to eat. Some ask that you simply leave your tray table down as a sign you want to be woken up for the service while others provide you with stickers to let the crew know your preference of sleep vs. food:

Often, at the start of the flight, the crew will announce the times at which they'll be serving meals or you may find this info on a menu (if they hand one out) or in the inflight magazine (e.g. Korean Air). 

Normally meals are shortly after departure and/or shortly before landing. If you want to eat the first meal you can simply stay awake until it is served. For the final meal, the crew normally has to wake most everyone up for landing to check seatbelts, etc. so they just do it a bit earlier to do the meal service - all the lights turn on and there is a lot of noise and people moving about in the cabin so you may wake up.

Really long flights, especially daytime flights, may feature additional mid-flight snacks. These are easier to miss since the crew tries to let those opting to sleep rest. However, the crew is normally flexible about these, the food served is typically less perishable, and you'll likely easily be able to get this snack later if you slept through the service and wake up hungry - just ask nicely.

Some airlines have come up with a solutions to the conflict of some passengers wanting to sleep and others wanting to be woken up to eat. Some ask that you simply leave your tray table down as a sign you want to be woken up for the service while others provide you with stickers to let the crew know your preference of sleep vs. food:

Normally, at the start of the flight, the crew will announce the times at which they'll be serving meals. Normally the first meal is shortly after departure and/or shortly before landing. If you want to eat the first meal you can simply stay awake until it is served. For the final meal the crew normally has to wake most everyone up for landing to check seatbelts, etc. so they just do it a bit earlier to do the meal service. Normally all the lights turn on and it there is a lot of noise and people moving about in the cabin so it's hard to sleep.

Missing mid-flight meals or snacks on long haul flights can be an issue though. The crew is normally flexible about these and will easily be able to give you your later if you slept through the service and wake up hungry.

Some airlines have come up with a solutions to the conflict of some passengers wanting to sleep and others wanting to be woken up to eat. Some ask that you simply leave your tray table down as a sign you want to be woken up for the service while others provide you with stickers to let the crew know your prefernce of sleep vs. food:

Often, at the start of the flight, the crew will announce the times at which they'll be serving meals. Normally the meals are shortly after departure and/or shortly before landing. If you want to eat the first meal you can simply stay awake until it is served. For the final meal, the crew normally has to wake most everyone up for landing to check seatbelts, etc. so they just do it a bit earlier to do the meal service - all the lights turn on and it there is a lot of noise and people moving about in the cabin so it's hard to sleep. Many flights tend to try to match service the arrival time to help with jet lag, often the service will be as soon as possible for allow passengers who wish to sleep as long an interrupted period as possible. There is sometimes a paper menu provided at each seat with some hints about meal times like "dinner" (you can surmise what might be a reasonable time range in either the origin or destination), "pre-arrival snack", etc.

Missing mid-flight meals or snacks on long haul flights is easier than missing the services close to departure and arrival. However, the crew is normally flexible about these, the food served is typically less perishable, and you'll likely easily be able to get this snack later if you slept through the service and wake up hungry.

Some airlines have come up with a solutions to the conflict of some passengers wanting to sleep and others wanting to be woken up to eat. Some ask that you simply leave your tray table down as a sign you want to be woken up for the service while others provide you with stickers to let the crew know your preference of sleep vs. food: