You can earn up to 100,000 miles with the United Explorer Business card, but only for one more week

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• The United Explorer Business Card is currently offering its highest-ever sign-up bonus: up to 100,000 United miles. You'll earn 50,000 miles after spending $5,000 on purchases in the first three months, and another 50,000 miles after spending $25,000 total on purchases in the first six months.
• That's a high spending requirement, but keep in mind that this is a small-business credit card.
• Based on The Points Guy's valuations, 100,000 United miles are worth $1,300.
• You only have until October 10 to apply and lock in this elevated sign-up bonus; after that date, the offer will probably decrease.
• Read more personal finance coverage.

Airline credit cards haven't always been the most lucrative type of rewards credit card - historically, they trailed behind travel cards like the Chase Sapphire Preferred Card in terms of the rewards they offered on a wide range of purchases. But lately they've been looking extra competitive, as credit card issuers have added new perks and more opportunities to earn bonus rewards on everyday spending.

This applies to small-business airline credit cards as well as their consumer counterparts. One great option is the United Explorer Business card, which has a $95 annual fee and earns 2 miles per dollar not only on United purchases, but also at restaurants, gas stations, and office supply stores.

Currently, the United Explorer Business card is offering new cardholders up to 100,000 United miles as a sign-up bonus. You'll earn 50,000 miles after you spend $5,000 in the first three months, and another 50,000 miles after you spend $25,000 total in the first three months.

However, this offer is ending on October 10, so time is running out if you're interested in taking advantage of it.

Keep in mind that we're focusing on the rewards and perks that make these credit cards great options, not things like interest rates and late fees, which can far outweigh the value of any rewards.

When you're working to earn credit card rewards, it's important to practice financial discipline, like paying your balances off in full each month, making payments on time, and not spending more than you can afford to pay back. Basically, treat your credit card like a debit card.

Why choose the United Explorer Business card?

If you're a business traveler loyal to United Airlines, this card offers a number of useful benefits:

• A free checked bag on United
• Priority boarding on United
• 2 one-time United Club airport lounge passes each year after your account anniversary

These benefits are in addition to the miles you'll earn on your spending, and the sign-up bonus. And speaking of that welcome offer, according to The Points Guy, United miles are worth 1.3 cents apiece, which means the full 100,00-mile bonus is worth $1,300.

The United Explorer Business card has no foreign transaction fees, so you can use it abroad without worrying about incurring any extra charges.

Read more: The best credit card sign-up bonuses available now

Why choose a business credit card?

If you're a business owner, or even if you have a side gig to supplement income from your full-time job, separating your work and personal expenses is key to staying organized. You don't need to have a large company with dozens of employees to get approved for many small business cards, and if you are eligible to open a card like the United Explorer Business card, you'll benefit from perks that are tailored to business users, like bonus rewards at office supply stores.

Business credit cards often run lucrative sign-up bonuses, but as is the case with the United Explorer Business card, they often have higher spending requirements to match. You'll need to spend $25,000 in the first six months to earn the full 100,000 miles with this offer - a sum that would be unreasonable for most individuals, but could be easily attainable for businesses depending on their size. If you can't comfortably spend $25,000 in the first six months, don't - it's never worth spending more than you can afford just to earn points or miles, as the rewards you earn will be dwarfed by the interest you'll pay for carrying a balance.

Read more: The best small-business credit cards

Click here to learn more about the United Explorer Business card.

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Please note: While the offers mentioned above are accurate at the time of publication, they're subject to change at any time and may have changed, or may no longer be available.