If you have an American Express Membership Rewards account, you can transfer points to participating frequent travel programs. One such program is your Hawaiian Airlines HawaiianMiles account. Usually one Membership Rewards point equals one HawaiianMiles mile. So 1,000 American Express Membership Rewards points will yield 1,000 HawaiianMiles.
However, now through 6/30/2021, you can receive 25% more HawaiianMiles when you transfer Membership Rewards points to your HawaiianMiles account. So during this offer, 1,000 American Express Membership Rewards points will yield 1,250 HawaiianMiles.
If you are trying to accumulate HawaiianMiles right now, this may be something you may want to consider taking advantage of.