Industrial sales are now about 10% of our business and are led by automotive sales, primarily in high-end sports cars and carbon fiber wheels. Marine is a market with longer-term growth potential, especially so in lightweighting parts, such as mask that reduce reliance on fuel and reduce emissions by large ocean vessels, including crews and transport ships incorporating wind-assisted ship propulsion. We remain very disciplined about the industrial business we pursue. Our team target growth areas where we can differentiate our technology. Reflecting confidence in our return to growth and our capacity to generate strong cash in the coming years. The Hexcel Board announced yesterday, a 20% increase in our quarterly dividend, from $0.125 to $0.15 per share.
In February, we’re going to hold an Investor Day in New York and via webcast, where we will discuss our road map for innovation and market growth in the coming years, as well as providing our medium-term outlook for the company in relation to sales, EPS and cash generation. We’re looking forward to seeing many of you there. In the meantime, for 2024, as reported in our news release last night, we are guiding to $1.925 billion to $2.025 billion in sales, with adjusted diluted earnings per share of $2.10 to $2.30. We’re also guiding to greater than $200 million of free cash flow. Further details around 2024 will be provided in our Investor Day next month. Now, let me turn it over to Patrick to provide more details on the numbers.
Patrick Winterlich: Thank you, Nick. As a reminder, the majority of our sales are denominated in dollars. However, our cost base is a mix of dollars, euros and British pounds as we have a significant presence in Europe, including both manufacturing and R&D. As a result, when the dollar strengthens against the euro and the pound, our sales translate lower, while our costs also translate lower, leading to a net benefit to our margins. Conversely, a weak dollar is a headwind for our financial results. We hit this currency exposure over a 10-quarter horizon, protect our operating income. As a result, currency changes are laid into our financial results over time. As a reminder, the year-over-year sales comparison I will provide are in constant currency, which thereby remove the foreign exchange impact to sales.
Turning to our three markets. Commercial Aerospace represented approximately 60% of total fourth quarter 2023 sales. Fourth quarter Commercial Aerospace sales of $267.5 million increased 5.3% compared to the fourth quarter of 2022, led by strong growth in the Airbus A350 and Boeing 787 programs. Total fourth quarter narrowbody sales were lower year-over-year, including declines in Airbus A320neo, Airbus A320 and the Boeing 737 MAX program. The Other Commercial Aerospace category grew 2.3%, with continued growth in business jets, partially offset by softer sales in other markets served by this category. Space & Defense represented approximately 30% of fourth quarter sales and totaled $152.3 million, increasing 19.7% from the same period in 2022.
Classified programs grew strongly year-over-year and space programs were strong, including launches, rocket motors and satellites. European military and civilian helicopter sales also strengthened notably. Industrial comprised approximately 10% of the fourth quarter 2023 sales. Industrial sales totaled $37.7 million, decreasing 22.3%, compared to the fourth quarter of 2022. Sales grew strongly year-over-year in the performance-orientated automotive market, although this growth was more than offset with lower sales across our other industrial markets. On a consolidated basis, gross margin for the fourth quarter was 22.5%, compared to 23.1% last year. Similar to our commentary last quarter, we have invested ahead of our customers in order to support aircraft production rate rounds.
This involves spending on infrastructure, head count and higher levels of employee training. Demand pull-through for narrow-body programs, lower than we expected, is the near-term headwind, as the full cost of our increased infrastructure base was not absorbed by the actual sales level. This should lessen through the first half of 2024, as the overall narrowbody supply chain stabilizes to support the narrowbody rate ramps. As a percentage of sales, selling, general and administrative expenses and R&D expenses were 11.8% in the fourth quarter compared to 12.3% in the fourth quarter of 2022. We continue our strong focus on operating cost control as our top line grows to maximize volume leverage. Adjusted operating income in the fourth quarter was $49.1 million or 10.7% of sales, compared to $46.3 million or 10.8% of sales in the comparable prior year period.
