Earnings season rages on this week. Here are the 8 companies to watch - and what to look out for.

Hot off the news that it's acquiring Intel's modem business, Apple now needs to prove whether its slowing iPhone sales can recover and if its Services sector can maintain its robust growth.

Apple's last quarterly report saw sales fall 5%, with a 17% decline in iPhone revenue. The company has struggled to sell its phones in China and India as the trade war and high prices overseas help competitors sweep up market share.

The company reportedly asked for tariff exemptions for its new Mac Pro product to avoid greater trade-war fallout, but President Trump declined the request Friday.

Be sure to check the company's iPhone sales and Services growth once the report is out. Analysts say the Services business — which includes iCloud, Apple Music, and the App Store, among other apps — could make up for lagging computer and phone sales, so any large decline in that sector can spell danger for the company's future revenue stream.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $53.33 billion, versus $53.27 billion in the same period last year
• Earnings per share (GAAP): estimated $2.10, versus $2.34 in the same period last year

The combination of low unemployment, a strong US economy, and robust consumer confidence should play well for Mastercard heading into second-quarter earnings. Analysts expect the company's double-digit growth for digital payments to continue and help offset increased marketing costs.

The company may also detail its expectations for the Apple Card, a Mastercard collaboration the tech company is likely to release in August in partnership with Goldman Sachs. Mastercard may also continue its share buyback program from the first quarter of 2019, when it repurchased roughly 8.7 million shares worth about $1.8 billion.

Mastercard also has a penchant for stronger-than-expected quarterly results. The company has surpassed analyst estimates each quarter since the second quarter of 2015, with an average beat of 6.46%, according to Bloomberg data.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $4.08 billion, versus $3.67 billion in the same period last year
• Earnings per share (adjusted): estimated $1.83, versus $1.66 in the same period last year

Analysts expect Pfizer to report a year-over-year profit decline when it releases its next earnings report. The company started 2019 by splitting its commercial operations into three different businesses, and its second-quarter report should expand on how the reorganization has affected revenue.

Like with Amgen, investors will look to Pfizer's pipeline to see if it can deliver certain treatments before competitors. Pfizer and Merck are both looking to release an improved Prevnar pediatric vaccine.

Despite the former having released the latest version, investor worry Merck is ahead in the race to bring the newer version to market.

Keep an eye on Prevnar progress, drugs moving up Pfizer's pipeline, and any hints of recovering revenue growth when the company reports earnings Tuesday.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $13.40 billion, versus $13.47 billion in the same period last year
• Earnings per share (adjusted): estimated $0.75, versus $0.81 in the same period last year

All eyes are on Airbus to surge past Boeing in aircraft deliveries now that the latter company continues to suffer fallout from its 737 Max disaster.

Airbus delivered 150 more planes than Boeing in the first half of 2019, so its upcoming earnings report should expand on how the French company plans to maintain its lead over the world's largest planemaker.

Airbus' second-quarter report should also show greater profits from plane sales, with higher unit prices balancing out a dip in deliveries. The company is still recovering from a lag in engine production due to technical issues, so keep an eye out for Airbus delivering its nearly-complete planes after building up its inventory in past quarters.

The manufacturer also recently closed a deal with Bombardier to build its C Series planes. The transaction could boost yearly guidance and send the stock higher.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated 17.39 billion EUR, versus 14.85 billion EUR in the same period last year
• Earnings per share (adjusted): estimated 1.482 EUR, versus 0.582 EUR in the same period last year

Coming off a week that included AT&T's earnings report and the Justice Department's approval of the T-Mobile/Sprint merger, Verizon has much to address. The company is in the midst of rolling out its 5G network, paying $4.3 billion to launch the tech in 30 US cities by the end of 2019.

Verizon doesn't plan to see revenue from 5G until 2020, as most consumers won't have 5G compatible phones until then. However, the company's earnings call may expand on the revenue growth Verizon anticipates from 5G.

Verizon also boosted its yearly earnings outlook in its first-quarter report, so investors will want to know if the company remains on track or if revenue growth is stagnating.

The telecom company plans to collect $10 billion in cumulative cash savings by 2021. The program has yielded about $3 billion as of Verizon's first-quarter report, so any acceleration for the initiative may spur investor interest.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $32.41 billion, versus $32.20 billion in the same period last year
• Earnings per share (adjusted): estimated $1.20, versus $1.20 in the same period last year

Warren Buffet's empire firm saw its first-quarter earnings deviate substantially from last year's figures due to a new accounting rule, so this week's report should bring more clarity to Berkshire Hathaway's 2019 performance.

The first-quarter report also omitted earnings from the company's stake in Kraft Heinz, a 27% investment Buffet said he "overpaid" for in his February letter.

Berkshire also loosened its share buyback policy in 2018. Buffet said in his annual letter the company could spend as much as $100 billion in a repurchasing program. Such a move would signal to investors that Buffett sees Berkshire's holdings as more valuable than the current book value.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $66.26 billion, versus $62.20 billion in the same period last year
• Earnings per share (Class B): estimated $2.58, versus $2.79 in the same period last year

While energy giants like Royal Dutch Shell and Total invest more in electric energy and renewable power, ExxonMobil has doubled down on its oil and natural gas businesses. It's also the most financially sound of companies in its sector, with lower debt than its competitors.

Exxon's Friday earnings call should detail how successful the company's bet on sturdy oil demand has been, and whether it will join its peers in pivoting to greener ventures.

Prices of Brent oil have fallen 9% year-over-year in the second quarter, providing key insight into how the gas company's report may read.

However, the company's offshore sites in the Guyana and Permian regions grew in the first quarter, despite its quarterly figures falling behind estimates in April.

Here are Wall Street's quarterly estimates heading into the week:

• Revenue: estimated $65.81 billion, versus $73.50 billion in the same period last year
• Earnings per share (adjusted): estimated $0.69, versus $0.92 in the same period last year