Shares of many airlines and cruise operators were lower this past week due to concern about the continued spread of the delta variant of COVID-19.

The virus variant has been spreading rapidly in parts of Asia, including Japan where the Olympics will begin Friday, elsewhere around the world.

The Dow Jones Industrial Average on Monday posted its worst day of 2021. Stocks plummeted, finishing broadly and sharply lower as investors moved into safe-haven assets and weighed how rising COVID-19 cases might affect the economic recovery in the U.S. and globally.

The Dow finished down 725 points, or 2.09%, at 33,962, the S&P 500 dropped 1.59% and the Nasdaq slumped 1.06%. At their lowest levels on Monday, the Dow blue chips slumped 946 points or 2.7%, the S&P 500 gave back 2.2% and the Nasdaq fell 1.7%.

Over on Real Money, Jim Cramer writes that there's "too much speculation, too little stability in the face of a COVID rebound." It's a revolt of the buyers, he says, mixed with a strong belief that the Delta variant will take away all the upside of the speculative economy. Want more of his real-time market analysis? Read his list of factors that continue to weigh on stocks, and how investors can protect their portfolios.

Airlines such as United Airlines  (UAL) - Get United Airlines Holdings, Inc. Report and American Airlines  (AAL) - Get American Airlines Group, Inc. Report and cruise lines like Norwegian Cruise Line Holdings  (NCLH) - Get Norwegian Cruise Line Holdings Ltd. Report were among the biggest losers. They tumbled on fears about the spread of the COVID-19 delta variant and worries that new lockdown restrictions will stall the economic rebound.

However, TheStreet's Jim Cramer said from the floor of the New York Stock Exchange: "You have to start buying here simply because you don't know when the bottom's going to be."

Here are several stocks that fell this past week and could present an opportunity to buy the dip.

1. Virgin Galactic | -20.50% Past Week | -12.09% 1 Month

Virgin Galactic  (SPCE) - Get Virgin Galactic Report shares continued to fall a week after the aerospace company founded by the entrepreneur Richard Branson said in a filing that it may sell up to $500 million of stock. Branson recently completed a test flight into space and Amazon's  (AMZN) - Get Amazon.com, Inc. Report Jeff Bezos is scheduled to take his first space flight on Tuesday.

TheStreet does not have a Quant Rating rating for Virgin Galactic.

2. Norwegian Cruise Lines | -19.79% Past Week | -27.79% 1 Month

Norwegian Cruise Lines  (NCLH) - Get Norwegian Cruise Line Holdings Ltd. Report, which filed an amicus brief in this case, is suing Florida Surgeon General Scott Rivkees for the right to require all passengers to be vaccinated against COVID-19 once it restarts its Florida cruises on Aug. 15. Florida sued the CDC in April, claiming the agency’s restrictions on the cruise industry during the pandemic effectively blocked most cruises and harmed the state’s livelihood.

TheStreet Quant Ratings rates Norwegian Cruise Lines as a Sell with a rating score of D.

3. AMC Entertainment | -18.69% Past Week | -41.54% 1 Month

AMC Entertainment  (AMC) - Get AMC Entertainment Holdings, Inc. Class A Report and a group of 36 other meme stocks have fallen as much as 4.4%, according to Bloomberg, marking a sixth straight decline, after the group's worst week since late February. Earlier this month, AMC scrapped plans to have shareholders approve a planned capital increase that would have diluted existing stockholders.

TheStreet Quant Ratings rates AMC Entertainment as a Sell with a rating score of E+.

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4. Carnival Corp. | -17.35% Past Week | -30.02% 1 Month

It has not been an easy run for Carnival Cruise  (CCL) - Get Carnival Corporation Report. The Miami cruise operator's shares are down about 2% on Thursday, but that’s much better than the 5.2% loss the stock was sporting at the recent low. Carnival fell in late June when it said it planned to raise another $500 million. It fell again when it reduced its debt a few days later.

TheStreet Quant Ratings rates Carnival as a Sell with a rating score of D.

5. Royal Caribbean | -14.83% Past Week | -18.90% 1 Month

Royal Caribbean  (RCL) - Get Royal Caribbean Cruises Ltd. Report, in collaboration with the Florida Division of Emergency Management (FDEM), docked its Explorer of the Seas vessel at the Port of Miami to provide free housing and support for the search-and-rescue teams working at the Surfside condo collapse. 

TheStreet Quant Ratings rates Royal Caribbean as a Sell with a rating score of D.

6. United Airlines | -14.20% Past Week | +20.92% 1 Month

United Airlines Holdings  (UAL) - Get United Airlines Holdings, Inc. Report is among the air carriers and cruise-line operators that slumped due to concern about the continued spread of the delta variant of COVID-19. 

TheStreet Quant Ratings rates United Airlines as a Sell with a rating score of D+.

7. Boeing Co. | -13.17% Past Week | -12.82% 1 Month

Boeing Co.  (BA) - Get Boeing Company Report shares slumped lower Tuesday after the plane maker said it would trim production of its 787 Dreamliner following the discovery of structural flaws in the troubled twin-aisle aircraft. The company said it would deliver "fewer than half" of the 787s currently in inventory by the end of the year, down from its prior forecast of "the vast majority" as it works with the Federal Aviation Administration to fix gaps in what is known as the forward pressure bulkhead.

TheStreet Quant Ratings rates Boeing as a Sell with a rating score of D.

8. MGM Resorts International | -11.86% Past Week | -10.41% 1 Month

MGM Resorts International  (MGM) - Get MGM Resorts International (MGM) Report agreed to buy Infinity World Development's 50% interest in CityCenter Holdings for $2.125 billion. The agreement will make MGM Resorts the 100% owner of CityCenter on the Las Vegas Strip, a complex made up of Aria Resort & Casino and Vdara Hotel and Spa.

TheStreet Quant Ratings rates MGM Resorts as a Sell with a rating score of C-.

9. Coinbase Global | -10.89% Past Week | -3.75% 1 Month

Cathie Wood-led ARK Investment Management  (ARK)  shed shares in chipmaker Nvidia  (NVDA) - Get NVIDIA Corporation Report and e-commerce back-end provider Shopify  (SHOP) - Get Shopify, Inc. Class A Report, shifting some of its capital into Coinbase Global  (COIN)  amid a dip in the crypto exchange provider’s stock price. The investment firm snapped up 27,844 shares, estimated to be worth about $6.77 million, in cryptocurrency exchange Coinbase on the dip, according to reports.

TheStreet does not have a Quant Rating rating for Coinbase Global.

10. Delta Airlines | -10.06% Past Week | -14.28% 1 Month

Delta Air Lines  (DAL) - Get Delta Air Lines, Inc. Report rose this past week before slumping after Raymond James analyst Savanthi Syth double-upgraded the air carrier to strong buy from market perform with a $58 price target following an earnings call. Also, Morgan Stanley analyst Ravi Shanker, who kept an overweight rating and $73 price target, said the shares deserve to be trading "significantly higher than current levels."

TheStreet does not have a Quant Rating rating for Skillz.

NOTE: Recently, Quantitative Analysis by TheStreet Quant Ratings objectively rated these stocks according to their risk-adjusted total return prospect over a 12-month investment horizon. Not based on the news on any given day, the rating may differ from Cramer's view or that of this articles' author.