What are ‘can’ and ‘could’?
We use can to talk about ability now — something we are able to do today. We use could to talk about ability in the past — something we were able to do before, or were not able to do. Both words go directly before the main verb, without ‘to’.
These sentences come from a story about how satellite Wi-Fi is changing aviation:
- Passengers can now connect to fast internet during their flight. (present ability)
- Before Starlink, passengers could not watch films or join video calls. (past inability)
Formula: subject + can / could + verb (without to)
A common mistake to avoid
Many learners add to after can or could. This is incorrect:
- ✗ Passengers can to connect to the internet.
- ✓ Passengers can connect to the internet.
Always use can or could with the bare infinitive — the verb without to. For example: can fly, could reach, could not offer.
Fill in the gaps
Type can or could in each space. Look for time signals — words like now, before, and in the past will help you choose.
Passengers _____ now connect to fast internet anywhere on the flight.
‘Can’ expresses ability in the present. The word ‘now’ tells you this is a current ability, not a past one.
Before Starlink, airlines _____ not offer fast internet to their passengers.
‘Could not’ means ‘was not able to’. ‘Before Starlink’ tells you this is about the past.
The satellite system _____ reach speeds of up to 500 megabits per second.
‘Can’ describes a general, present ability — what the system is able to do right now.
In the past, passengers _____ not watch films or join video calls on most flights.
‘Could not’ means ‘was not able to’. The phrase ‘In the past’ signals a past situation.
Business travellers _____ now answer emails and join meetings from the air.
‘Can’ + ‘now’ describes a new, current ability made possible by satellite technology.
Before this change, loyalty members _____ only get Wi-Fi by paying for it.
‘Could’ describes what was possible in the past. ‘Before this change’ is the time signal.
Now make it real
Think about your work in aviation or your experience as a passenger. Write two sentences — one using can (a present ability) and one using could not (a past inability).
Before you check the answers, read your sentences and ask yourself:
- Did I use can for something possible today?
- Did I use could not for something that was impossible before?
- Did I write can / could without ‘to’? For example: can fly, not can to fly.
- Does my sentence make sense in a real aviation context?
These are samples to compare with your own — not the only possible answers.
I can now answer emails and join calls during long-haul flights, thanks to satellite Wi-Fi. Before this technology, I could not communicate with my team from the air.
Passengers can connect to the internet free of charge with an Alaska Airlines loyalty account. In the past, they could only pay for slow, expensive Wi-Fi.
Now improve your sentences. Can you add a time phrase — for example, today, in the past, or before this change?
CEFR Level A2 / ICAO Level 3
Once you are comfortable with can and could, explore the difference in Structure: ‘can & could vs be able to’ — in formal aviation English, the differences between these forms matter.