Shares of wholesale juggernaut Costco (NASDAQ:COST) declined about 1.2% during after-hours trading as of 7 p.m. EDT. Meanwhile, shares of JetBlue (NASDAQ:JBLU) rose 0.5% -- and that was on top of a 3.6% gain during the trading day. The volatility in these stocks follows updates from both companies. Costco reported its March sales data and JetBlue said it plans to launch routes to London.

Costco's March sales

In March, Costco's net sales rose 7.4% year over year to $13.87 billion. Notably, however, the period benefited from one extra shopping day compared with the same month last year because of the calendar shift of Easter. "This positively impacted total and comparable sales by approximately one to one and one-half percent," management said in the company's sales update. 

A shopping cart in the aisle of a wholesale store.

Image source: Getty Images.

Same-store sales (also called comparable sales) for the period rose 5.7%. When excluding the impact of gasoline prices, foreign exchange rates, and a change to the way the company recognizes revenue, same-store sales were up 6.9%. This adjusted same-store sales growth was comprised of 5.5% growth in the U.S., 6.7% growth in Canada, and 7.4% growth in Costco's "other international" segment.

Adjusted e-commerce sales were up 20.1% year over year, highlighting the channel's continued importance to the company's growth story. While this was strong compared with Costco's overall sales growth, it was a slowdown from adjusted growth of 21.6% year over year in February.

JetBlue's new routes

During the trading day, JetBlue's stock moved higher as the company said traffic in March increased 7.9% year over year. Capacity was up 12.6%. The growth was higher than management was expecting. 

But optimism persisted for the stock in after-hours trading when the company announced plans for its first routes to London. The routes will originate from both New York and Boston. "London is the largest metro area JetBlue doesn't yet serve from both Boston and New York," said JetBlue COO Joanna Geraghty in a press release about the new routes.

The company is convinced its value proposition for these new routes to Europe will be compelling. It plans to position itself between "sky-high fares -- particularly in premium cabins" and "a handful of low-cost carriers ... with a no-frills, bare-bones approach to flying," the company said. "Particularly in Europe, JetBlue will raise the bar on what travelers can expect from a low-cost carrier."

JetBlue plans to offer multiple daily flights from both cities, beginning in 2021.