Delta Flights: Cash, Miles, Certificates or Credits?

To book a Delta flight, you can pay with cash (credit/debit card), redeem SkyMiles, use an eCredit, or apply a travel certificate, and the best choice depends on the fare price, your mileage balance, and whether you have a companion certificate or a refundable credit expiring soon. This guide breaks down how each payment method works, how to combine them, and how to decide which one saves you the most money or miles on a given itinerary.

Formula

This calculator helps you compare a cash fare against a SkyMiles award redemption. The key formulas are:

• Cash cost = ticket price (what you’d pay with a card).
• Miles needed for award = ticket price × 100 (Delta’s standard rate of 100 SkyMiles per $1 for most domestic awards).
• Value of miles used = (miles needed ÷ 1000) × your assumed value per 1,000 miles.
• Miles left after award = your current balance − miles needed.

Variables: t = ticket price in USD, m = your SkyMiles balance, v = your assumed dollar value per 1,000 SkyMiles (typically $10–$20).

Worked Example

Suppose a round-trip main cabin ticket costs $450, you have 50,000 SkyMiles, and you value miles at $15 per 1,000 miles.

1. Cash cost = $450.
2. Miles needed = 450 × 100 = 45,000 miles.
3. Value of miles used = (45,000 ÷ 1000) × 15 = $675.
4. Miles left = 50,000 − 45,000 = 5,000 miles.

So redeeming miles for this ticket would use 45,000 miles, leaving 5,000. If you value 45,000 miles at $675, that’s more than the $450 cash price, so paying cash is the better deal unless you have a specific reason to use miles (like using up miles before devaluation).

Background: How Delta Payment Methods Work

Delta lets you pay for flights in four main ways: cash (credit/debit), SkyMiles, eCredits (from canceled flights), and travel certificates (like companion certificates or customer satisfaction vouchers). Each has its own rules.

• Cash – The most flexible. You earn SkyMiles on the purchase (unless you buy basic economy).
• SkyMiles – Redeem miles for award tickets. You still pay taxes and fees (usually $5.60–$100+ for international).
• eCredit – A non-refundable credit from a canceled flight. Must be used by the original ticket’s expiration date, often one year from issue.
• Travel Certificate – A promo code or voucher (e.g., $100 off, companion pass). Often has blackout dates and must be used in one transaction.

How to Combine Cash, Miles, and Credits

Delta’s system is not fully flexible. You cannot mix cash and miles in the same transaction for a standard award ticket – it’s either all miles or all cash. However, you can apply an eCredit or certificate to a cash fare, and you can pay taxes on an award ticket with a credit card. You cannot apply an eCredit to an award ticket’s taxes.

If you have a companion certificate (from a Delta credit card), you can use it on a cash fare only, and you pay the taxes and fees for the companion. You cannot use miles for the main ticket and the certificate for the companion on the same reservation.

How to Choose: Cash vs. Miles vs. Certificate

Here’s a practical decision tree:

1. If you have an eCredit or certificate that expires soon, use it first – it’s essentially free money that vanishes.
2. If you have a companion certificate, compare the total cost with the certificate (fare for one + taxes for both) vs. paying cash for both. Usually the certificate wins if the fare is high.
3. If you’re considering miles, calculate the cents-per-mile value: (cash price − taxes) ÷ miles needed. If that value is above your personal threshold (often 1.5–2 cents), use miles; otherwise pay cash.
4. If you have a large mileage balance and a low cash fare, paying cash preserves miles for future high-value redemptions.

Common Problems and Misconceptions

Many travelers assume that miles are always the best deal, but that’s not true. Delta uses dynamic pricing for awards, so the miles required can be much higher than the 100-per-dollar baseline. Also, eCredits are non-transferable and can’t be used for basic economy. A common misconception: you can’t use an eCredit to pay for a companion certificate’s taxes – you can, but only if the certificate is applied to a cash fare and the eCredit covers the remaining balance.

Another issue: if you cancel a flight paid with an eCredit, you get a new eCredit for the same amount, but the expiration date may not extend. Always check the new expiration.

Costs and Fees to Watch

Cash fares earn SkyMiles at 5x per dollar for general members (more for Medallion status). Award tickets earn no miles. Award tickets also require you to pay taxes and carrier-imposed fees, which can be significant on international flights. eCredits have no additional fees, but if the new fare is lower, you get a residual eCredit; if higher, you pay the difference with a card. Certificates often have a dollar minimum (e.g., $250 fare before taxes) and may not apply to basic economy.

Alternatives to Consider

If you have a Delta credit card, you may get a free checked bag and priority boarding, which can tip the scale toward cash. Also consider using a travel portal (like Chase or Amex) to transfer points to SkyMiles, but that usually locks you into the same award rules. If you have a companion certificate, it’s often the single best value – a round-trip companion ticket for taxes only. Don’t forget that you can also use a combination of an eCredit and a credit card on a single cash booking, but you cannot split payment between two cards or between a card and a certificate in the same transaction (you must use one form of payment per reservation).

Frequently Asked Questions

Can I use an eCredit to pay for a SkyMiles award ticket?
No. eCredits can only be applied to cash fares. You cannot use them to cover the taxes or fees on an award ticket.

What happens if my eCredit expires?
It becomes worthless. Delta does not typically extend eCredits, though during some disruptions (like the COVID-19 pandemic) they did. Always book before the expiration date.

Can I combine a companion certificate with an eCredit?
Yes, but only if the eCredit is used as the payment method for the cash fare that the companion certificate is applied to. The certificate reduces the fare, and the eCredit covers the remaining amount.

How do I know if I’m getting good value for my miles?
Divide the cash price (minus taxes) by the miles required. If you get 1.5 cents per mile or more, it’s generally a good redemption. For example, a $450 ticket for 45,000 miles gives 1 cent per mile, which is poor.

Can I pay for a Delta flight with a mix of cash and miles?
No, Delta does not allow split payments between cash and miles for a single ticket. You must choose one form of payment. However, you can use a credit card to pay taxes on an award ticket.

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in t | Ticket price ($) | USD | 450 | 0
in m | SkyMiles balance | miles | 50000 | 0
in v | Miles value per 1000 | USD | 15 | 0 | 100
out cash | Cash cost (USD) | USD | t | 2
out miles_needed | Miles needed for award | miles | t * 100 | 0
out miles_value | Value of miles used (USD) | USD | (t * 100 / 1000) * v | 2
out leftover | Miles left after award | miles | m - t * 100 | 0