It’s great that we have loads of regular verbs in English, because once we know the rules on how to conjugate one regular verb we can conjugate all the others. e.g. I walk, I walked, I’m walking, etc. But that would be too easy for the foreigners, which is why the English language also uses irregular verbs. It keeps people like me in business!
By their nature, because irregular verbs are irregular, you will just have to learn the ones you use the most often and get used to their irregularities. It’s no use me explaining the logic behind what makes a verb regular or irregular – it’s just the way it is okay!
However, with some irregular verbs, it is increasingly common for their use to become regular over time. As such you can use them in a regular form, even though – strictly speaking – this is not formal British English grammar.
So, in the example ‘I learnt to fly yesterday’, is the proper use of the past tense form of ‘to learn’. However, ‘I learned to fly yesterday’ can also be used.
Verbs such as ‘dream’, and ‘spell’ can also be used in this way, especially in the US, where grammar standards have slipped to an all-time low. (yes I am only joking).