American Express is offering a 30% transfer bonus to Virgin Atlantic through May 31, 2016. For the next four weeks, 1,000 Membership Rewards will transfer to 1,300 Etihad Guest Miles.

This is huge news because there is also currently a 30% discount on Virgin Atlantic economy awards through May 11, 2016. Combining this transfer bonus with that sale means you can book awards from the Eastern United United States to London for 10,000 Membership Rewards plus $135 with great availability for the next 11 months if you act right now.

Today only: Frontier is offering a fare sale for Summer and Fall travel. Fares start at $21 one way!

The sale is valid for bookings made by 11:59 PM ET today (June 30) for domestic, nonstop travel on Tuesdays, Wednesday, and Saturdays between August 22 and December 16. Blackout dates are November 19 to December 1.

Here is the sale page and restrictions.

Today only: Frontier is offering a fare sale for Summer and Fall travel. Fares start at $21 one way!

The sale is valid for bookings made by 11:59 PM ET today (June 30) for domestic, nonstop travel on Tuesdays, Wednesday, and Saturdays between August 22 and December 16. Blackout dates are November 19 to December 1.

Here is the sale page and restrictions.

Update 6/30 at 1 PM ET: Stack this sale with the promo code 24OFF.

It offers $12 off per one way and $24 of per roundtrip. But on the $23/$34 fares, it only offers 1 cent off. On the $58 fares, it offers the full $12 off. The cut off point is somewhere in between.

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Through today June 30, Spirit is selling tickets for July and August starting at $23.10 one way for members of its "$9 Fare Club" and $34.10 one way for non-members.

Update 6/30 at 1 PM ET: Stack this sale with the promo code 24OFF.

It offers $12 off per one way and $24 of per roundtrip. But on the $23/$34 fares, it only offers 1 cent off. On the $58 fares, it offers the full $12 off. The cut off point is somewhere in between.

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Through today June 30, Spirit is selling tickets for July and August starting at $23.10 one way for members of its "$9 Fare Club" and $34.10 one way for non-members.

Update June 24: United added this promo to its promo page. Book by July 6.

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United is offering up to a 25% discount on roundtrip awards to Hawaii for travel this Summer and Fall!

United cardholders get a 25% discount and pay 33,750 United miles roundtrip to Hawaii. Non-cardholders get a 20% discount and pay 36,000 United miles roundtrip. Full price is 22,500 United miles one way in economy between Hawaii and the continental United States, Alaska, or Canada.

The sale is valid:

for roundtrip or open jaw awards.

Southwest is offering $49, $99, $129, and $149 one way fares if you book by tomorrow (June 4) and fly between August 25 and December 16. Fridays, Sundays, September 3-5, September 7, and November 20 - December 1, 2015 are blacked out.

For other restrictions and all the city pairs, see the sale page. Here are the $49 fares from Baltimore:

There are even a few sale prices under $49.

If you prefer to fly with another carrier, check to see if they are matching the sale.

Frontier’s Summer sale ends today. Fares start at $29 one way!

The sale is valid for bookings made by 11:59 PM ET on May 29 for domestic, nonstop travel mostly on Tuesdays, Wednesdays, and Saturdays between June 2 and August 12.

Here is the sale page and restrictions.

Delta now offers awards within the United States for as little as 10,000 miles one way in economy. Previously the minimum price for a domestic award was 12,500 miles (or at least I think it was, since Delta doesn't have an award chart anymore.) From the press release:
New One-Way Award tickets beginning as low as 10,000 miles plus taxes and fees, available through Dec. 31, 2015 for travel in select U.S., Mexican and Caribbean markets.