Atmus Filtration Technologies Set to Join S&P SmallCap 600

Atmus Filtration Technologies (NYSE:ATMU) will be added to the S&P SmallCap 600 and will replace Air Lease (NYSE:AL) effective prior to the open of trading on April 9, 2026.

Rhea-AI Summary

Atmus Filtration Technologies (NYSE:ATMU) will be added to the S&P SmallCap 600 and will replace Air Lease (NYSE:AL) effective prior to the open of trading on April 9, 2026.

S&P Dow Jones Indices said the table of index changes lists ATMU as an addition and AL as a deletion on that effective date; a Sumitomo Corporation & consortium acquisition of Air Lease is expected to close pending final conditions.

Positive

• ATMU added to S&P SmallCap 600 effective April 9, 2026
• AL removed from S&P SmallCap 600 effective April 9, 2026
• Acquisition pending for Air Lease by Sumitomo & consortium, per announcement

Negative

• Index exclusion for AL effective April 9, 2026
• AL acquisition remains subject to final closing conditions

Argus Apr 6 session

+0.05% close to close Open Argus

Details

News Market Reaction – AL

In the Apr 6 session, AL gained 0.05%, reflecting a mild positive market reaction.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement confirms that Air Lease will be deleted from the S&P SmallCap 600 as Atmus Filtrat...

Analysis

This announcement confirms that Air Lease will be deleted from the S&P SmallCap 600 as Atmus Filtration is added, reflecting the pending acquisition and expected delisting. It follows prior disclosures about the cash merger terms and final regulatory approval, indicating the transaction is approaching completion. Investors tracking this situation may focus on the effective index-change date, announced closing timing, and any remaining conditions to the merger’s completion.

Key Figures

Index change effective date: April 9, 2026

Index change effective date

April 9, 2026

Effective prior to the open for S&P SmallCap 600 changes

Historical Context

5 past events · Latest: Mar 30

5 events

1. Mar 30

   Merger approval

   24h Move

   +0.3%

   Final regulatory approval for cash merger at $65.00 per share.

2. Feb 12

   Earnings results

   24h Move

   +0.1%

   Record Q4 and FY2025 revenues and net income with strong fleet metrics.

3. Jan 26

   Fleet delivery

   24h Move

   -0.1%

   First of five Boeing 737-8 aircraft delivered to Air Canada on lease.

4. Jan 8

   Fleet activity update

   24h Move

   +0.1%

   Q4 2025 update with deliveries, sales, and sizable aircraft investments.

5. Dec 19

   Aircraft delivery

   24h Move

   +0.1%

   First of four Airbus A321XLR deliveries to Qanot Sharq on long-term lease.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

s&p smallcap 600, nyse, gics sector, s&p 500, +1 more

5 terms

s&p smallcap 600 financial

"Atmus Filtration Technologies Inc. (NYSE: ATMU) will replace Air Lease Corp. (NYSE: AL) in the S&P SmallCap 600"

A stock market index made up of 600 small-cap U.S. companies chosen to represent the performance of smaller publicly traded firms. It matters to investors because it acts like a temperature gauge for the small-company segment of the market, serving as a benchmark for fund managers, a basis for index funds and ETFs, and a way to compare returns and risk when building a diversified portfolio.

nyse financial

"Atmus Filtration Technologies Inc. (NYSE: ATMU) will replace Air Lease Corp. (NYSE: AL)"

A large, regulated marketplace where stocks and other securities are listed and traded, acting like a global auction house that matches buyers and sellers and helps determine share prices. It matters to investors because listing and trading there provide liquidity, price discovery, and regulatory oversight—making it easier to buy or sell holdings and giving companies a visible platform that can affect credibility and access to capital.

View in glossary

gics sector financial

"Effective Date | Index Name | Action | Company Name | Ticker | GICS Sector"

GICS sector is one of the major industry groupings from the Global Industry Classification Standard, a system that sorts companies into consistent categories (like Technology or Health Care) based on the primary business they do. Investors use these sectors like folders in a filing cabinet to compare companies, build diversified portfolios, and track how whole parts of the market are performing rather than focusing on single stocks.

s&p 500 financial

"such as the S&P 500® and the Dow Jones Industrial Average®."

The S&P 500 is a broad stock market index that tracks the performance of 500 large U.S. companies, weighted so bigger firms have a larger impact. Investors use it like a thermometer or benchmark to judge how the overall U.S. stock market or a portfolio is doing; movements in the index influence investor sentiment, fund performance, and many passive investment products that aim to match its returns.

View in glossary

dow jones industrial average financial

"such as the S&P 500® and the Dow Jones Industrial Average®."

A stock market index that tracks the share prices of a small group of large, well-known companies to give a quick snapshot of how the broader market is doing. Think of it like a thermometer for the stock market: it uses a handful of heavyweight firms as representative samples to show whether investor sentiment is rising or falling, which helps investors gauge market trends and compare performance over time.

View in glossary

AI-generated analysis. How Rhea-AI works. Not financial advice.

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NEW YORK, April 2, 2026 /PRNewswire/ -- Atmus Filtration Technologies Inc. (NYSE: ATMU) will replace Air Lease Corp. (NYSE: AL) in the S&P SmallCap 600 effective prior to the opening of trading on Thursday, April 9. Sumitomo Corporation & Consortium are acquiring Air Lease Corp in a deal expected to be completed soon, pending final closing conditions.

Following is a summary of the changes that will take place prior to the open of trading on the effective date:

Effective Date	Index Name		Action	Company Name	Ticker	GICS Sector
April 9, 2026	S&P SmallCap 600	Addition		Atmus Filtration Technologies	ATMU	Industrials
April 9, 2026	S&P SmallCap 600	Deletion		Air Lease	AL	Industrials

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S&P Dow Jones Indices is a division of S&P Global (NYSE: SPGI), which provides essential intelligence for individuals, companies, and governments to make decisions with confidence. For more information, visit www.spglobal.com/spdji/en/. 

FOR MORE INFORMATION:

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View original content:https://www.prnewswire.com/news-releases/atmus-filtration-technologies-set-to-join-sp-smallcap-600-302733292.html

SOURCE S&P Dow Jones Indices

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

When will Atmus Filtration Technologies (ATMU) join the S&P SmallCap 600?

ATMU will join the S&P SmallCap 600 effective prior to the open on April 9, 2026. According to S&P Dow Jones Indices, the change lists ATMU as an addition and will take effect before trading begins that day.

Why is Air Lease (AL) being removed from the S&P SmallCap 600 on April 9, 2026?

Air Lease is being deleted from the S&P SmallCap 600 effective April 9, 2026. According to S&P Dow Jones Indices, the deletion coincides with a pending acquisition by Sumitomo Corporation and a consortium.

Does the press release say the Sumitomo acquisition of Air Lease (AL) is complete?

No, the acquisition is not complete; it is expected to close pending final conditions. According to S&P Dow Jones Indices, the deal is anticipated to be completed soon but remains subject to closing requirements.

What is the effective date for both the ATMU addition and AL deletion from S&P SmallCap 600?

Both the addition of ATMU and deletion of AL are effective prior to the open of trading on April 9, 2026. According to S&P Dow Jones Indices, the table of index changes lists that effective date for both actions.

Which sectors are listed for Atmus (ATMU) and Air Lease (AL) in the index change?

Both companies are listed under the Industrials GICS sector in the index update. According to S&P Dow Jones Indices, the table shows ATMU and AL assigned to Industrials for the April 9, 2026 changes.