The U.S. economy has proven to be remarkably resilient despite the tough macroeconomic environment. Although the Federal Reserve's 16-month fight against soaring inflation has taken benchmark interest rates to the highest level in 22 years, the U.S. economy has posted an unexpected 2.4% year-over-year growth rate in the April-to-June quarter. This was mainly driven by a 7.7% year-over-year jump in business spending (excluding housing).

Given these factors, many analysts believe that we may now be in the early stages of a bull market. Hence, it makes sense to buy stocks of fundamentally strong companies such as Microsoft (MSFT 1.82%) and Airbnb (ABNB 0.75%) that stand to grow rapidly during times of economic expansion.

Let's assess these companies in greater detail.

Microsoft

The second-largest company in the world by market capitalization, Microsoft exceeded top- and bottom-line consensus analyst expectations in the fourth quarter of its fiscal 2023 (ended June 30). The company reported a healthy 8% year-over-year jump in revenue to $56.2 billion while operating income grew by 18% to $24 billion.

Shares of Microsoft are currently up by nearly 41% so far this year. While this is a solid jump for a blue-chip stock, there are a few reasons why this growth momentum can continue in the coming months.

First, Microsoft has played a key role in ushering the current generative artificial intelligence (AI) boom -- thanks to its investments (around $13 billion) in the widely famous ChatGPT developer, OpenAI. The company has integrated AI capabilities into several of its offerings such as the Bing search engine, Azure cloud platform, and Microsoft 365 suite -- to make them technologically cutting-edge, improve performance, and reduce costs.

The company has also teamed up with Advanced Micro Devices to develop AI chips that can compete with those of Nvidia.

Plus, Microsoft is now working on monetizing its AI capabilities. In July, the company unveiled its decision to charge users $30 per month for Microsoft 365 Copilot, an AI assistant for the Microsoft 365 office productivity suite. This aggressive pricing is expected to boost the company's revenue and operating income in future quarters.

Microsoft also continues to ride multiple tailwinds in the cloud computing space. Its Azure cloud business accounted for over half of the $110 billion of cloud revenue, or nearly $55 billion, in fiscal 2023. This implies a year-over-year jump of at least 62%. The integration of AI chatbot capabilities and Azure cloud computing services, called Azure OpenAI Service, should further help the company gain market share.

Cybersecurity is also emerging as a major growth driver for Microsoft. Although it's currently a small portion of the overall business, the company has already built a large catalogue of cybersecurity products that provide endpoint security, identity protection, identity-centric secure web gateway for the internet, and zero-trust network access.

Microsoft has been gaining momentum in this area and ended the fourth quarter with over 1 million enterprise clients, 26% more on a year-over-year basis. Of these, 60% use four or more security products, which is indicative of the competitive edge of the offerings and the stickiness of its customer base. The company will also make Security Copilot -- which integrates next-generation AI into security operations -- available to customers in the coming fall.

Besides the many factors that can propel its stock, Microsoft also returned $38 billion to shareholders as dividends and share repurchases in fiscal 2023. Given the robust fundamentals of the stock, you'll be thanking yourself for buying it in the long run.

Airbnb

Vacation rental leader Airbnb's share prices are up by over 79% so far this year. However, with demand in the travel industry rebounding, the company's shares may rise even more in the coming months.

Airbnb noted a rising number of active bookers for current and future trips, increasing cross-border travel (in North America and the Asia-Pacific region), and rising demand in high-density urban locations in the first quarter. The company also saw an increasing number of guests using Airbnb accommodations for long-term stays (28 days or more).

Since the company's platform acts as an intermediary between guests (people seeking out rental properties) and hosts (people renting properties), Airbnb has emerged as a major beneficiary of these improving demand trends. The company's asset-light business model has enabled it to expand the supply of properties -- in urban and non-urban locations across the world -- rapidly, in line with the rising demand.

Airbnb has been consistently attracting new hosts and customers through continuous platform upgrades, new features, and innovations. The company has built a solid brand name in the online travel industry with its commitment to high-quality booking experiences.

The company also benefits from network effects, since high-quality hosts help attract new customers, while more customers entice hosts to list their properties on the platform. This flywheel effect is also helping the company rapidly build its presence in several underpenetrated markets.

Airbnb is a highly profitable and cash-flow-rich business. Hence, patient investors can take advantage of this business and consider buying a small position in this stock now.