Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The Dow Jones Industrials (^DJI 1.08%) has bounced back slightly today, with gains of about 62 points as of 12:30 p.m. EST giving investors a welcome respite from the declines we've seen in recent days. Yet in the middle of earnings season, market conditions can change in an instant, and AT&T (T -0.10%) and Boeing (BA -0.68%) are on deck to give their latest results. What AT&T says about prospects in the telecom industry and what Boeing adds on the aerospace front could have dramatic implications for the Dow and the stock market in general.

AT&T reports this afternoon after the market closes; results are likely to come shortly after 4 p.m. EST, with a 4:30 p.m. conference call scheduled to discuss the numbers. Boeing investors will likely see its report at about 7:30 a.m. tomorrow, based on when the company has traditionally issued its press release, with a conference call to follow at 10:30 a.m. EST.

In the AT&T earnings report, investors will anxiously await the latest numbers on the telecom giant's sales of smartphones, especially its share of iPhone sales following Apple's report of weaker than expected volume for its device during the past three months. At the same time, though, shareholders have been nervous about the stock's relatively weak performance, and even its 5.5% yield isn't reassuring investors that AT&T has the growth capacity to move forward strongly. Moreover, increased competition from smaller participants in the industry could pose a long-term threat to AT&T, particularly given that many of those rivals are specifically targeting the company rather than fellow giant Verizon. Investors will want to see longer-term strategic plans that show AT&T's intent to hold off its rivals and find innovative new offerings of its own.

Meanwhile, for Boeing earnings, the aerospace giant has been in control of its own destiny for years, as airline demand has picked up impressively and driven huge order growth. Now the biggest challenge that Boeing faces is delivering on its order obligations, especially as new orders just keep coming in. Yet with one major labor issue resolved, Boeing can return its full attention toward making manufacturing-efficiency improvements that could speed production and help it add to earnings growth sooner.

Between its high share price and its unique position as one of the dominant commercial aircraft manufacturers in the world, Boeing is more likely to have an outsized impact on the Dow than AT&T. Yet both companies could move the blue-chip index if they deliver surprising news -- especially if one or the other fails to meet the expectations that investors have for their respective success.